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Old 04-07-2015, 06:21 PM   #1
gpshumway
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Default The NASIOC Oil Selection Guide

1. Introduction

Standard Disclaimer:
This guide is not an official Subaru document, and does not represent direct technical advice from the author, it is opinion and for information only. If you have an engine failure after reading this, don't blame me or anyone else at NASIOC.

TL;DR Readers:
Readers with A.D.D. are advised to skip to the engine specific recommendations and specific oils sections at the end of this guide, but be warned, forum members and moderators will not treat kindly new threads asking questions which are answered here.

Ron (Unabomber) has done a wonderful job with all of his FAQs including the one on oil. Despite Ron’s best efforts we continue to see frequent “best oil” and “how good is this oil?” threads. With the advent of the FA and FB series of engines from Subaru and their substantially different design from the older EJ engines, it seems time to provide some updated information and a basis for oil selection in different applications and driving conditions. In his FAQ Ron offers his opinion as to which oils are “best” if you were to press him on the subject. While there are very good reasons for his selections, Ron did not enumerate them in his FAQ. This guide is not intended to supplant Ron’s information, but augment it by providing a detailed discussion of motor oil and its properties. It is the intent of this guide to provide the background information required for a reasonably competent layperson to select a “good” oil for their application. This process consists mostly of understanding what categories exist for motor oil and selecting an oil from the right category, the performance differences between oils in the same category are generally so small as to be immeasurable outside a laboratory. Because of this it is impossible for laypersons to determine which oil is “best”. Even professionals with the tools and knowledge to do such analysis generally don't have the time or resources. If you take nothing else from this guide, it should be to stop focusing on brand and “best” so you can think more about category and “good”.

This guide is a combination of information gleaned from various internet sources, industry organizations and companies involved with making and testing motor oil. I am not a lubrication engineer or tribologist, merely a technically savvy enthusiast. Much of this guide consists of my opinion which is based upon the imperfect information available to the general public. As such, reasonable people will undoubtedly disagree with my assessments. That’s fine, I’m certainly willing to learn from others and hopefully fill some of the large void of information surrounding motor oil. Your comments are welcome and appreciated, but please keep it civil and remember that much of the available information is imperfect at best. Please feel free to point out any inaccuracies or glaring omissions.

We will start by discussing the basics of engine lubrication and the physical properties of motor oil, move to the specifications which control those properties and define the categories modern oils fit into. We'll briefly discuss used oil analysis as a tool for confirming and fine tuning a selection, and finally we'll examine what Subaru recommends for their cars and use all that information to select the correct category of oil for our unique situation. This guide will generally illustrate how to select oils based upon technical requirements, and will only obliquely address concerns over warranty coverage. Subaru's recommendations for oil will be the starting point for selection, but some reading between the lines of the simplistically written owner's manuals will be required. For most users technical and warranty requirements coincide nicely, but for many owners of performance Subarus there is some cause for concern. We will address these concerns in a specific section on warranty requirements.
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Old 04-07-2015, 06:21 PM   #2
gpshumway
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2 Engine Lubrication Basics

In order to select good oil for our application we must first understand its function within the engine. Modern four stroke automotive piston engines have an “active” lubrication system consisting of a positive displacement oil pump and passageways throughout the engine which deliver oil from the pump to the engine’s functional elements. This oil system is an ancillary system in the engine, a vital one for sure, but not essential to the engine’s primary function. It is entirely possible to design an engine without an oil pump, two-stroke outboard motors and four-stroke lawnmowers are two examples. An oil’s ability to be drawn from the pan and pumped through the engine are primary concerns of the specifications governing motor oil which we’ll discuss later.

Oil’s first and foremost job is to prevent wear within the engine, it does this in two ways, by providing a hydrodynamic film which completely separates moving parts from each other, and by providing chemical anti-wear compounds which prevent wear between parts in contact. These compounds take the form of additives dissolved in the oil and are largely independent of the oil’s viscosity (thickness), which determines its hydrodynamic properties. Which anti-wear mechanism is functioning depends on the state of lubrication at a particular interface inside the engine. Hydrodynamic lubrication has already been mentioned, the two other states are boundary and mixed-film. In boundary lubrication the surfaces are in contact and the anti-wear additives in the oil are primarily responsible for preventing wear. Mixed film is –you guessed it- the transition condition between boundary and hydrodynamic.

You can read more here:
http://www.stle.org/resources/lubelearn/lubrication/

Contrary to popular belief, oil pressure supplied by the oil pump does not provide hydrodynamic lubrication in the engine. The hydrodynamic wedge which separates a rotating shaft from its journal bearing is a result only of the oil’s viscosity and the rotational speed of the shaft. As long as the oil pump supplies enough oil to keep the bearing full of oil, no additional pressure is necessary. Think of a water-skier or a hydroplaning tire, the water in each case is not supplied under pressure, yet both the skier and the tire are suspended above the solid surface below.

Why do we worry about oil pressure if it doesn't indicate lubrication quality then? Well, “proper” oil pressure is an easy to measure indication of a healthy engine and oil system, if it falls outside of normal parameters, it indicates that something is wrong. If it drops precipitously, something is very wrong. Oil pressure is a result of the oil’s viscosity, flow rate, and the size of the orifices which it is being forced through, and viscosity is highly dependent on temperature, so slightly low oil pressure can be an indication that the oil is too hot. Oil pressure also drops as the clearances in the engine increase through wear, particularly the clearances within the oil pump itself. Oil pressure which drops precipitously indicates a failure of the lubrication system, most often the pickup becomes uncovered (usually through high-g cornering) and the system draws air instead of oil, but the pressure can also drop quickly due to a sudden mechanical failure like a broken oil pump drive, or an oil gallery plug that comes out. If the 2psi oil pressure idiot light in your Subaru turns on, you have only a couple of seconds to turn the engine off or face catastrophic failure. Note: don't confuse the oil pressure idiot light with the oil level idiot light on newer cars. The implications of the level light are not nearly as severe.

While not essential to hydrodynamic lubrication, oil pressure may be necessary to activate variable valve timing mechanisms or other functions within the engine, in this case the oil is functioning as a hydraulic fluid, not a lubricant, which brings up the topic of secondary functions. In addition to lubrication, the oil also must also be: a coolant, a corrosion inhibitor, a detergent, an acid neutralizer and sometimes a hydraulic fluid. Most of these functions are not handled solely by the oil itself, but by compounds dissolved in it as part of the additive package.

Main crankshaft bearings, big end connecting rod bearings and camshaft bearings are designed for hydrodynamic lubrication, but many interfaces within the engine are reciprocating, not rotating, and therefore do not generate the consistent velocity required for hydrodynamic lubrication. These interfaces experience mixed-film or boundary lubrication conditions, and rely on the oil's anti-wear additives to prevent wear. Despite the seemingly undesirable lubrication condition, these components last for hundreds of thousands of miles in a modern engine. Engineers think about states of lubrication as regions of the Stribeck curve (fig 1), named for the engineer who invented it. The vertical axis is friction and the horizontal is either speed (assuming constant viscosity) or viscosity (assuming constant speed). Because speed is a function of the engine's bearing sizes and RPM, set by the designers, we'll concern ourselves only with Stribeck curves with viscosity as the independent variable. When selecting an oil for your Subaru, the shape of the curve at the transition between hydrodynamic and mixed-film regimes are important to keep in mind.



Figure 1 – The Stribeck Curve
1 – Boundary lubrication
2 – Mixed film lubrication
3 – Hydrodynamic lubrication

http://www.tribology-abc.com/abc/stribeck.htm

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Old 04-07-2015, 06:22 PM   #3
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3 Motor Oil Properties

When selecting oil we're mostly selecting an oil with the best physical properties for our application, which of course requires defining those properties. Motor oil behaves differently under variations of temperature and mechanical stress, so a wide variety of tests are used to fully characterize its physical properties. Governing specifications place limits on these properties which an oil must meet, and vehicle manufacturers call out these specifications in owner's manuals as requirements of proper maintenance.

3.1 Viscosity
We've already talked a little about viscosity, and most car enthusiasts have some idea what it is; explicitly, viscosity is the scientifically measured “thickness” of a fluid. The stereotypical molasses in January has a very high viscosity, while water has a low viscosity. Oil viscosity is measured in several ways, dynamic, kinematic, and at varying temperatures. This is done because the viscosity properties of oil depend greatly on temperature and the physical stress imposed. Ideal “Newtonian” fluids have very predictable viscosity properties which can be calculated easily, but motor oil is a non-Newtonian fluid so engineers measure its viscosity under varying conditions in order to develop a full picture of how it will perform in service. Motor oil is generally a shear-thinning non-Newtonian fluid, meaning it has a lower viscosity in fast moving parts than in slow moving parts. This Wikipedia entry gives an overview of different types of viscosity and what makes a fluid Newtonain. http://en.wikipedia.org/wiki/Viscosity
Dynamic Viscosity
Dynamic viscosity is the most basic measure of a fluid’s thickness, it indicates the fluid’s resistance to shearing. The theoretical model for dynamic viscosity is two large plates of material separated by a thin film of fluid, one plate is stationary, the other moving. The amount of force required to keep the moving plate at a particular velocity determines the dynamic viscosity. A detailed explanation of dynamic viscosity is not in the scope of this guide, but the above Wikipedia entry gives an explanation.

Kinematic Viscosity
Kinematic viscosity is a fluid’s dynamic viscosity divided by its density, it is convenient to measure in gravity driven test fixtures. Motor oil’s kinematic viscosity is commonly measured at 100°C (KV100) and 40°C (KV40), the former is the basis for the SAE grades of motor oil we’re all used to seeing (e.g. 5w30). In motor oil, kinematic viscosity is highly dependent on temperature.

Viscosity Index (VI)
The viscosity index is a derivative of the oil’s KV100 and KV40 set against an arbitrary scale. It gives an indication of an oil’s viscosity variation with temperature at moderate and high temperatures. It does not characterize oil viscosity behavior at extremely low temperatures, nor under high rates of shear. An oil with a higher viscosity index will show smaller variations in viscosity with variations in temperature than an oil with a low viscosity index. Knowing the KV100 and KV40 (and hence the VI) allows us to use the standard mathematical model to approximate an oils kinematic viscosity across a range of temperatures from about 32°F to 300°F. Below 31°F the formation of crystals can cause the oil to increase viscosity much faster than the equations would predict, and extrapolating beyond 300°F is unwise.

An online calculator for viscosity index is available here:
http://www.widman.biz/English/Calculators/VI.html

High Temperature-High Shear Viscosity (HT/HS)
HT/HS is a measure of dynamic viscosity, it represents the oil’s thickness within the vital hydrodynamic bearings of an engine. It is the most important measure of how well the oil will perform as a hydrodynamic lubricant. HT/HS is measured at 150°C (302°F) which is a worst-case temperature for most engines. The higher the HT/HS, the stronger the hydrodynamic film in the engine’s bearings. Thus, the correct HT/HS is more important than the KV100 (SAE Grade) when selecting oil. If the oil formulator publishes their HT/HS it's best to ignore the grade and KV100 and base your choice on the HT/HS. As we will see later, different industry specs categorizing motor oil are based in large part on HT/HS and those specifications will tell us much about the oil's HT/HS even if the formulator doesn't publish a specific value.

Low Temperature Cranking Viscosity (CCS Viscosity)
Cranking viscosity is measured in a Cold Cranking Simulator (CCS) at a temperature corresponding to the oil’s SAE Grade. The CCS measures the oil’s resistance to being pumped through the engine when very cold. Oils with lower CCS viscosities require less power from the starter to achieve sufficient RPM to start the engine - the lower the CCS viscosity, the easier the engine will start at very cold temperatures. Depending on the SAE grade, CCS is measured between -31 °F (0w) and 14°F (25w).

Low Temperature Pumping Viscosity (MRV Viscosity)
Pumping viscosity is measured in a mini-rotary viscometer (MRV), it indicates the oil’s resistance to being drawn into the oil pump when very cold. Oils with lower MRV viscosity are more easily drawn from the oil pan into the pump. This is important because oil which is too hard to draw into the pump will cause cavitation and the pump will ingest air instead of oil. Air makes a lousy hydrodynamic lubricant, so failed main bearings are the inevitable result of cavitation. The lower the MRV viscosity the greater the safety margin against cavitation.

Pour Point
Pour point is a sort of viscosity. It is the lowest temperature at which the oil will flow under prescribed conditions. You can think of this as the “freezing” temperature for oil as 0°C is the freezing temperature of water. Water is a homogeneous substance composed only of H2O molecules, so it has a definite freezing temperature (32°F), oil is a heterogeneous soup of molecules varying in weight and composition, so it doesn’t turn solid at a definite temperature. It never the less starts forming crystal structures at some temperature at which point further cooling causes the viscosity to increase much faster. This point of accelerating viscosity increase is what the pour point intends to measure. Pour point has largely been supplanted by MRV and CCS as a measure of oil’s extreme cold performance, but many manufacturers still publish pour points for their oils any way.

This Mobil 1 video shows a non-scientific pour point test:
https://www.youtube.com/watch?v=YnagT6wKfmY

Note this test is conducted with 5w30 oil at -40°C, which is much colder than 5w30 is intended to be used in an engine.

Temporary Shear
When oil is subjected to high shear stress, as when sandwiched between the crankshaft and main bearings, oil exhibits lower viscosity than would be predicted by measuring that viscosity in a slow moving fixture. Once the oil leaves the high shear area and returns to the pan, its viscosity returns to normal. This characteristic is known as temporary shear thinning, and the oil's resistance to it is an important performance characteristic. The ratio between an oil's low shear viscosity and its high shear viscosity is known as its temporary shear ratio. Oil formulators don't publish the temporary shear ratio for their oils, and very few publish specifications which would allow you to calculate it, but many oils have available specifications which allow one calculate an approximation.

Shear Stability
Often confused with temporary shear is permanent shear. Some constituents of oil, particularly Viscosity Index Improvers (VIIs), change their chemical makeup when subjected to repeated cycles of physical shearing. The physical stress of shearing “clips” the longer molecules into shorter ones, thus permanently reducing the oil's viscosity. In many oils designed to improve fuel economy this effect can be quite pronounced, often reducing the oil's viscosity by 10% or more and resulting in a reduction in viscosity grade from 30 to 20 or 40 to 30. An oil's resistance to permanent shear is known as its shear stability. Motor oil certification specifications set minimum levels of shear stability with the European ACEA specs being more stringent than the American API/ILSAC specs.

3.2 Other Properties

Specific Gravity
This is the density of the oil relative to water (1=water), it is published by many manufacturers on their product data sheets. A normal user has no use for it, but advanced users might use it in a calculation to estimate the temporary shear ratio of an oil. Those calculations are beyond the scope of this guide.

Flash Point
Flash point is the lowest temperature at which the oil will generate sufficient vapor to catch fire if exposed to an ignition source. The flash point of virgin oil is compared to that of used oil in an oil analysis. Contaminants in the oil like unburned fuel lower an oil’s flash point.

Blackstone Labs Explains Flashpoint here: (http://www.blackstone-labs.com/what-...lash-point.php)

Volitility (NOACK)
The NOACK test measures the percentage of oil lost to evaporation at 250°C, a temperature consistent with the highest temperatures seen at the top piston ring. Lighter constituent elements in oil tend to evaporate first, leaving the remaining oil thicker, which can affect its cold weather properties during extended use. Evaporated elements of the oil can also affect combustion when burned. NOACK is given as a percentage of the oil which evaporates during the test. All other things equal, lower NOACK oils will show less consumption and more stable viscosity.

Total Base Number (TBN)
TBN is a measure of the oils ability to neutralize acidic contaminants. Acidic byproducts of combustion enter the oil via piston ring blow-by and must be neutralized before they damage engine components or the oil’s base stock. The higher the total base number, the more acid the oil can neutralize before being changed. Unfortunately, depletion of the TBN can be quite non-linear, especially with new technology oils using non-traditional additives, so an oil with a higher TBN may not allow for longer oil change intervals than one with a lower TBN.

Last edited by gpshumway; 04-07-2015 at 06:58 PM.
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Old 04-07-2015, 06:22 PM   #4
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4 Motor Oil Components – What’s in my oil?

The average user is neither a chemical engineer nor a tribologist, and therefore the actual chemical makeup of motor oil is not particularly useful to them. So why write this section? Primarily to debunk a lot of the misinformation surrounding what is good or bad about particular components of motor oil. Motor oil is composed of two basic components, a base stock and an additive package. Base stocks can be guessed reasonably accurately using the oil’s Material Safety Data Sheet (MSDS), but this is largely irrelevant to the end user because what we really care about is the oil’s ability to protect the engine, that ability is heavily influenced by the oil’s additive package, the constituents of which are closely guarded trade secrets. As such, you will not find this information in the public space and even if you could, it would require the knowledge of an experienced tribologist to evaluate. If you’re such a person, you should be writing this guide, not reading it. Nevertheless, we will briefly discuss the various constituents of oil as they are useful to understand in certain circumstances.

Base Stock
The base stock of makes up 80% or more of an oil’s total volume, they are classified by the American Petroleum Institute (API) into five groups. The groups are defined by the types of molecules which make up the base oil and by physical properties, they are designated by roman numerals I-V. Groups I, II and III are hydrocarbon base stocks, group IV is poly-alpha-olefins and group V is “everything else” which in the context of motor oil usually means esters. The exact chemical definitions of olefins, esters, etc is beyond the scope of this guide.

Which groups are synthetic? Funny you should ask, “synthetic” is a marketing term, not a technical one. To the extent it could be considered technical it would mean that the base stock was synthesized from component elements. In other words “synthetic” is a process, not a physical property, and we’re trying to select finished oils with the right physical properties, we don't really care about the process used to make them. One could theoretically synthesize a really crappy base stock with poor physical properties, but nobody does because it’s cheaper to make crappy base stocks by refining crude oil. That said, we can make some reasonable generalizations.

Traditionally groups I and II are considered conventional petroleum oils while groups IV and V are synthetic, group III is the subject of great debate, especially among tribologists with a degree from Internet U. The latest group III base stocks made by the gas-to-liquids process certainly qualify as synthetic. The process involves sticking methane molecules (CH4) together until you get a hydrocarbon of the desired molecular weight, a textbook definition of synthesis. The resulting physical properties are excellent and every bit a match for the properties of traditional PAO or ester base stocks. The only area where PAO and ester stocks still hold an advantage over group III is at extremely cold temperatures irrelevant to most users, think Prudhoe Bay oil field workers and Antarctic researchers. Pennzoil products with “Pure Plus” marketed by Shell oil and some Mobil 1 products (Mobil’s not talking) are examples of gas-to-liquids Group III synthetic oils.

For a detailed look at base stock performance, see these (somewhat old) articles in Machinery Lubrication:
http://www.machinerylubrication.com/...oil-technology

Viscosity Index Improvers (VIIs)
As their name suggests, these additives improve the viscosity index of the base stock, reducing temperature's effect on the oil's viscosity. They are added to oil to help it meet cold start requirements. Unfortunately they carry negative side effects, they lower the oil's temporary shear ratio and they also tend to shear permanently, lowering the formulation's overall shear stability. This graph from Chevron/Oronite for their Paratone line of of VIIs shows how their effectiveness drops at high shear rates (temporary shear):


Figure 2
https://www.oronite.com/paratone/shearrates.aspx

Also from Chevron/Oronite, this graphic shows temporary and permanent shear.


Figure 3
https://www.oronite.com/paratone/shearloss.aspx

With modern synthetic base stocks it's possible to create 5w and 10w oils without any VIIs at all. The larger the “spread”, the harder this is to achieve, so a 10w30 oil is easier to formulate without VIIs than a 5w40.

Pour Point Modifiers
Pour point modifiers work to prevent crystal structure formation at temperatures approaching the oil's pour point, they have little effect at moderate and warm temperatures. They work in concert with VIIs to help an oil meet its cold start requirements, but do not carry all the negative side effects of VIIs.

Anti-wear Additives
Anti-wear additives are compounds dissolved in motor oil which form a sacrificial coating at the surface of moving parts which prevents wear of the base material. Contact with oil continuously refreshes this sacrificial layer, minimizing wear of engine parts in boundary and mixed film lubrication regimes. Traditional anti-wear additives are compounds of zinc, phosphorous and molybdenum. Newer anti-wear additives are compounds of antimony, boron, titanium, ceramics, and even organo-metallic compounds. The exact chemical forms and properties of these are beyond the scope of this guide, but it’s important to understand that they all require temperature to function. Their ineffectiveness at low temperatures is the source of the common knowledge that most engine wear occurs from cold starts. Many users believe the more anti-wear additives, the better, but increasing their concentration beyond a certain point does not reduce wear, and can lead to a reduction in the effectiveness of detergent additives and subsequently to sludge deposits.

http://www.bobistheoilguy.com/forums...mony_Additives
http://www.bobistheoilguy.com/forums...pics/1040691/1

Friction Modifiers
Friction modifiers are used in oils designed to improve fuel economy. Normally friction and wear are closely linked, but these additives don't really reduce wear. Some are multifunction additives like Molybdenum, which in high concentrations acts as a friction modifier. They can also interfere with the function of certain components, like the wet clutches in motorcycles, so they are specifically forbidden in certain oils.

http://www.infineum.com/Documents/Cr...ogy%202009.pdf

Anti-Oxidant Additives
Anti-oxidant additives help prevent the oil’s base stock from oxidizing and becoming thicker with use, which would hurt cold weather properties. Anti-wear compounds of Zinc and Phosphorous also function as anti-oxidants, their anti-oxidation function is the reason some oils have high concentrations of these additives. Modern base stocks are much more resistant to oxidation than their forebears, so less of these additives are required today.

http://www.bobistheoilguy.com/forums...ltifunctional_
http://www.bobistheoilguy.com/forums...ati#Post729355
http://www.chemeng.titech.ac.jp/~mma...tpindex_e.html

Detergents
These compounds prevent byproducts of combustion and degraded engine oil from turning into sludge deposits inside the engine. They break up and suspend the harmful compounds until the next oil change. Detergents are commonly compounds of Magnesium or Calcium. Detergents can compete with anti-wear additives for the surface of important components, so balancing them in the overall formula is important for best performance. When oil is ingested into the engine, the detergents can have a negative impact on the octane of the intake charge (they promote detonation). This is the reason oils marketed as pure racing oils have low levels of detergent and must be changed frequently. Detergents are often multifunctional serving also to neutralize acids.

Acid Neutralization Additives
The TBN property of motor oil is a result of acid neutralization additives. Some byproducts of combustion are acidic and those which end up in the sump through piston ring blow-by would attack the engine's metal components if not neutralized. The high degree of control afforded by modern fuel injection systems and the purity of modern fuels (particularly low sulphur) have made high levels of these additives less necessary. Some acid neutralizers also function as detergents.

Anti-Foaming agents
Some oils contain additives which help prevent the formation of small bubbles via the stirring action of the moving engine parts. Oil that’s been whipped into meringue by the crankshaft makes a lousy lubricant. These additives are often silicon compounds.

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Old 04-07-2015, 06:22 PM   #5
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5. Specifications Governing Oil
To ensure they will meet the needs of a modern engine, today's oils must meet testing and qualification criteria laid out in a myriad of industry specifications overseen by several industry groups. These specifications often specify minimum requirements, but no maximum, which makes it possible for several specifications to be met by the same oil. Understanding how various industry specifications overlap and combine to define how an oil will perform is the key to selecting the right oil for your application without being distracted by oil formulator's marketing messages.

5.1 SAE J300 (Viscosity Grade)
Society of Automotive Engineers (SAE) specification J300 is the source of the familiar grade designations we’re all used to seeing on motor oil (e.g. 5w30). All higher level industry specifications call upon J300 to define viscosity grades. Oil grades with a “w” in the middle are referred to as multi-grade oils, their low temperature performance is superior to the older straight grade (e.g. SAE 30) oils, which became very thick at low temperatures. The number before the “w” is the low temperature grade (w = winter) while the number after the “w” is the oil’s high temperature grade, sometimes referred to as the “weight” (e.g. 30 weight oil). Multi-grade oils must meet requirements for CCS viscosity, MRV viscosity, kinematic viscosity at 100°C (KV100) and HT/HS viscosity. Straight grade oils have to meet either MRV and CCS requirements, or HT/HS requirements, but not both. This handy table from Infineum summarizes the requirements of SAE J300. The table is from their larger oil classifications guide.


Figure 4
http://www.infineum.com/media/80723/...tions-2013.pdf

We'll ignore straight grades here as they would be dangerous to use in many circumstances, and modern base stocks and additives make multi-grade oils ubiquitous and high quality. SAE J300 was first written in the 1930s, a time when straight grades were often the best choice. You will notice that what defines a particular high temperature grade is KV100 in a particular range along with a minimum HT/HS viscosity (High-Shear-Rate Viscosity from the table). So, while the SAE grades provide useful general information about the oil’s viscosity properties, it’s possible for two very similar oils to be a different grade, a thick 30 grade can be very similar to a thin 40 grade. J300 splits oil grades into two general categories, “light duty” oils with HT/HS below 3.5, and “heavy duty” oils with HT/HS above 3.5, placing the split between 30 and 40 grade, but other specifications (ACEA) define a category of heavy duty 30 grade oils with HT/HS above 3.5.

The other thing to notice is the temperature requirements for the w number portion of multi-grade oils. The actual viscosity requirements for the w number are not that important, they’re arranged so an average car will start safely at the associated temperature, the temperatures therefore are the important bit. What they tell us is how cold a given grade of oil can be used safely. The cranking viscosity temperature represents a conservative minimum use temperature. So, 10w oils can be used down to -25°C (-13°F), 5w oils down to -30°C (-22°F), and 0w oils down to -35°C (-31°F – Brrr!). Also notice that the pumping viscosity requirements are always set 5°C lower than the cranking requirements, meaning the oil is always capable of being drawn into the oil pump if the starter is capable of turning the engine over, providing safety margin against cavitation.

There are many important properties not defined in J300 however: chemical properties, compatibility with seals and catalytic converters, and requirements for used engine oil. It is strictly a set of viscosity requirements for new oil. Those additional requirements are left to other specifications.

A note on grade designations; J300 specifies a dash be used in multi-grade oils (e.g. 5w-30) in this guide I will omit the dash for the reason that many forum search engines treat a dash as a space, and often refuse to search for terms shorter than three characters. So, searching for “5w-30” can be a major pain because the search engine treats it as two separate two letter words, “5w30” is easier to search for.

5.2 API Specifications
The American Petroleum Institute (API) defines a bewildering battery of requirements which ensure API certified oils meet the needs of a modern engine, including chemistry limits for beneficial and harmful constituents, tests for valvetrain wear, high temperature deposits, sludge formation, compatibility with seals and a whole host of other requirements. For many engines an oil of the appropriate SAE grade meeting the current API specifications is all that's needed to ensure durable operation. There are other specifications which we will see later have more stringent requirements which owners of high-performance cars may choose to seek in an effort to use the best oil possible, but any oil meeting the appropriate API specification and SAE grade will be a safe and effective lubricant.

The API specs are split into two groups, the service class (“S” series) for gasoline engines and the commercial ("C” series) for diesel engines. The API coordinates their efforts with the International Lubricant Standards Acceptance Committee (ILSAC) such that current versions of the API gasoline standards with their optional Resource Conserving designation (formerly Energy Conserving) are nearly equivalent to the current ILSAC standards. (i.e. API SN Resource Conserving = ILSAC GF-5) The Resource Conserving designation applies only to multi grade oils between 0w20 and 10w30 (and soon 0w16).

API Resource Conserving (API RC) requirements for fuel economy improvement are the strictest of any industry specification and vary by grade. 0w20 and 5w20 oils must make the greatest improvement, 0w30 and 5w30 less improvement, and 10w30 the least. Because the parasitic drag of the oil is directly proportional to its viscosity, API RC oils are often formulated toward the thin end of their viscosity grade, or designed to shear with use. The API requirements for shear stability are particularly weak for 30 grade oils, allowing them to shear to 8.5 cSt in the diesel fuel injector test. Because of this, API RC oils can be ill suited for some high performance applications like turbo EJ Subarus unless they carry additional shear stability requirements like those from the ACEA (see below).

The latest API service classes are SN (revision N) and CJ-4, with versions going back to SJ and CH maintained as current. The specifications are generally written to be backward compatible, so that an API SN oil can be used in cars which specified API SM, SL or even earlier in the owner's manual. This is true for performance requirements, but some chemical requirements have changed over time. With the introduction of API SM, reductions in the allowable amounts of zinc and phosphorous in 30 grade and thinner oils were implemented for emissions system durability reasons. Due to high levels of these additives, some Light Duty oils maintain their certification at API SL.

The API maintains a certification and licensing program which ensures quality and allows oil formulators to use the trademark “Donut” and “Starburst” symbols on their oil packaging. The Donut is printed on the back label of oil containers and is used for any current specification, the Starburst is reserved only for the latest S-series gasoline spec with Resource Conserving extension, and is placed on the front of the container. Under the API's licensing requirements formulators of engine oil may not market oil produced to non-current specs, but many un-ethical formulators do any way. The Petroleum Quality Institute of America (PQIA) runs a constant campaign to expose dangerously substandard oil for the benefit of consumers.


Figure 5 - The API “Donut”
http://api.org/~/media/files/certifi...glish_2013.pdf
All oils which carry the Starburst are Resource Conserving ILSAC certified oils conforming to the latest specifications at the time of manufacture. You may find some old oil on the shelf, but generally anything with a Starburst is a safe, current oil. Subaru bases the oil recommendations in their manual on the API Donut/Starburst requirements.


Figure 6 – the API/ILSAC “Starburst” (From the 2010 Impreza OM)

http://www.pqiamerica.com/apiserviceclass.htm
http://www.api.org/certification-pro...ust-fluid.aspx

5.3 ILSAC Specifications
The International Lubricant Standards Acceptance Committee (ILSAC) is a consortium of auto makers from the USA and Japan who write specifications for engine oil. Their requirements coordinate with and extend the basic API “S” series requirements, particularly in the area of fuel economy, but also in areas such as deposit formation. Unlike basic API 'S' oils which can be any SAE grade, ILSAC requirements apply only to Light Duty multi-grade oils from 0w20 to 10w30 (and soon to the new 0w16), Heavy Duty oils 40 grade and higher are not included in the ILSAC specs. The current specification is GF-5, and coordinates with API SN + Resource Conserving. All ILSAC GF-5 oils are API SN + Resource Conserving, but it's theoretically possible to make an oil which meets API SN + Resource Conserving, but does not meet ILSAC GF-5. In practice all commercially available oils which meet SN+RC also meet GF-5.

Additive maker Infineum publishes a handy chart which summarizes the API and ILSAC requirements (PDF)
http://www.infineum.com/media/80723/...tions-2013.pdf

5.4 ACEA Specifications
The Association des Constructeurs Européens d'Automobiles (ACEA) or in English, the European Automobile Manufacturers Association is the European equivalent of a combined API and ILSAC. They publish a comprehensive group of oil standards covering all categories of service for both gasoline and diesel engines. For many aspects of performance their standards are more stringent than the API/ILSAC specs. ACEA specs for engine performance are the most stringent of the commonly cited specifications.

The A/B categories are for passenger gasoline and light duty diesel engines, the E categories are for heavy duty diesels (think semi-trucks and earth movers), and the C categories place particular emphasis on emissions system compatibility in both gasoline and diesel engines. The C category is a class known as “Low-SAPS”, oils which have strict limits on content of Sulphated Ash, Phosphorous and Sulfur.

ACEA certifications claimed by formulators are supposed to include the year of issue (i.e. ACEA A5/B5-10 for the 2010 issue of the A5/B5 requirements) or if no year is denoted, they are to conform to the latest issue at the time the claim is made by the formulator. Unfortunately many formulators make claims which do not conform to the ACEA's guidelines seemingly without repercussions. ACEA requirements have always been very stringent, but have become even more so since 2008, so oils which carry the latest 2010 and 2012 certifications must be very high quality indeed.

A/B series
All A/B series oils are intended for use in both gasoline and diesel engines at long to very long service intervals. All sub-categories require 20 and 30 grade oils to stay within their original grade when subject to a shear stability test consisting of being squirted 30 times through a diesel fuel injector. These oils have moderate to high levels of SAPS additives and are suitable for very long drain intervals, some European manufacturers specify up to 20,000 miles on these oils.

A1/B1: For engines designed to use low viscosity Light Duty oils with a HT/HS viscosity of 2.6 - 2.8 for 20 grade and 2.9 - 3.5 for all other viscosity grades. 40 grade A1/B1 oils are the only ACEA oils allowed to thin out of their original grade in the shear stability test. With the 2012 revision of the ACEA standards A1/B1 wear standards are now the same as A5/B5 and A3/B4, slightly more stringent than in 2010. A1/B1 and A3/B3 standards for piston cleanliness and sludge are less stringent than for A3/B4 and A5/B5.

A3/B3: For high performance engines engines requiring HT/HS over 3.5. A3/B3 specifications for engine wear are slightly less stringent than A3/B4, A1/B1 or A5/B5, but still stricter than API/ILSAC. A1/B1 and A3/B3 standards for piston cleanliness and sludge are less stringent than for A3/B4 and A5/B5.

A3/B4: For high performance engines requiring HT/HS over 3.5. A5/B5, A1/B1 and A3/B4 specifications for engine wear are identical and slightly more stringent than for A3/B3. A3/B4 and A5/B5 standards for piston cleanliness and sludge are more stringent than those in A1/B1 and A3/B3.

A5/B5: For gasoline engines and car & light van diesel engines designed to be capable of using low friction low viscosity oils with a HT/HS viscosity between 2.9 and 3.5 mPa.s. Similar to A1/B1 but without provisions for 20 grade oils and with increased requirements for piston cleanliness and sludge resistance. A1/B1, A5/B5 and A3/B4 specifications for engine wear are identical and slightly more stringent than for and A3/B3. A3/B4 and A5/B5 standards for piston cleanliness and sludge are more stringent than those in A1/B1 and A3/B3.

E- Series
E series oils are intended for heavy duty diesel engines in machinery like over the road trucks and earth moving equipment. The distinction between these oils and the passenger car oriented A/B series has blurred over the years as governments have tightened the emissions requirements for heavy diesels to be more in line with passenger cars. This series is relevant to Subaru owners because several oils meet specs both for gasoline passenger cars and HD diesels, and therefore must meet the strictest requirements for both. With the exception of the E4 category which uses the A/B series shear stability test, all E-series oils must pass a shear stability test which is three times longer than for the A/B series (90 cycles vs 30). The two relevant E series categories for Subaru owners are E7 and E9, they are nearly interchangeable from the perspective of a gasoline engine, E7 might allow for longer oil change intervals, but E9 has lower levels of additives which might be harmful to emissions equipment. Either will have excellent shear stability.

C-Series
The C-series is a newer class of Low-SAPS oils with strict limits on ash, phosphorous and sulfur. The resulting oils are very similar to the A/B series, but must be changed at shorter intervals. The existence of this series is driven by the advent of diesel particulate filters which are very sensitive to clogging with burned oil byproducts. Where the A/B series can last up to 20,000 miles in gasoline engines, C-series oils normally max out at 10,000. In regards to engine performance, C1 and C2 are similar to A5/B5, while C3 and C4 are similar to A3/B3/B4.

http://www.acea.be/publications/arti...sequences-2012

For most specifications, Lubrizol's “Relative Performance Tool” is a great way to compare various aspects of performance:
http://lubrizol.com/EngineOilAdditiv...l/default.html

5.5 Manufacturer Specifications
In addition to industry groups, many manufacturers write their own specifications for motor oil to be used in their engines. Unlike the industry specifications, the underlying requirements of manufacturer specifications are usually not available to the general public, it is therefore difficult to use such specifications as a criteria for oil selection unless your particular car requires an oil which meets a manufacturer specification. What we can assume from the presence of manufacturers specifications is that none of the available industry specifications was stringent enough to meet the manufacturer’s requirements. So, if we see an oil which meets both the industry specs required by Subaru and some manufacturers specs, we can assume that oil meets requirements more stringent than industry specs. Whether those extra capabilities are relevant to our application is an open question. Many European manufacturer specifications are derivations and extensions of ACEA categories. North American and Asian manufacturer specifications tend to be extensions of ILSAC and API specifications.

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6. Categories
These categories are based on those defined by the ACEA for use in gasoline and diesel engines of either light or heavy duty nature. As Subaru doesn't make diesel engines for North America, we will concern ourselves mostly with the gasoline categories, and only refer to diesel categories if their requirements are relevant in a gasoline engine. It's important to understand that many of these categories are not mutually exclusive, it's possible to meet the requirements of more than one category at a time. For instance, EJ turbo engine favorite Shell Rotella T6 5w40 oil is designed and marketed for heavy duty diesel engines in the ACEA E9 category, but also meets API SM requirements for use in gasoline engines. Generally speaking all oils within a category will perform similarly, but these categories being arbitrary, some oils which push the borders of their category may be a wiser choice under certain circumstances.

Light and Heavy Duty Engine oils
Years ago engines were clearly delineated between the “heavy duty” engines in commercial vehicles like semi-trucks and earth moving equipment and the “light duty” engines in passenger cars and light trucks. The engines in these vehicles generally used different oil, light duty vehicles used Light Duty oils (30 grade or lower) and heavy duty vehicles used Heavy Duty oils (40 grade or higher). There were some exceptions like high performance cars with flat-tappet engines which used HD oil, but the rule generally held. Today there are many applications where the oil does not match the vehicle, many light vehicles use heavy oil and some heavy vehicles use light oil. So while the names have lost their descriptive value for the application, they still describe the oil's relative viscosity, Heavy Duty oils are thicker than Light Duty ones. The confusion comes with 30 grade oils which can be either Light or Heavy Duty.

The key characteristic of Light Duty oils is a HT/HS viscosity under 3.5. Light Duty oils come in SAE grades 30 and below, including all multi-grades. The focus of these oils is generally on maximizing fuel economy in passenger car and light truck applications. A common sub-category of Light Duty oils is API Resource Conserving/ILSAC oils, which can be thought of as “super-light” duty oils. These must meet additional fuel economy requirements that non-RC oils of the same grade do not. All Resource Conserving/ILSAC oils are Light Duty oils, but not all Light Duty oils are Resource Conserving, 20 grade oils marketed as “high mileage” are a common example. The majority of oils found on the shelves of your local retailer will be Light Duty. Specifications which address Light Duty oils are API S with or without Resource Conserving extension, ILSAC GF-x, ACEA A1/B1, ACEA A5/B5, ACEA C1 and ACEA C2.

Heavy duty oils are found in straight and multi-grades starting at 30 grade and going up. In passenger cars HD oils tend to be specified by European manufacturers. Their defining characteristic is a HT/HS viscosity above 3.5. SAE J300 only requires HT/HS greater than 3.5 in 40 grade and above oils, but ACEA A3/B3, A3/B4, C3, C4, E7 and E9 require 30 grade oils to have HT/HS greater than 3.5. Many OEM specifications from European manufacturers also specify 30 grade oils with HT/HS>3.5. SAE J300 requires 15w40 and thicker oils to have HT/HS of 3.7 or greater.

So, when we combine Light and Heavy Duty categories with available grades we get six oil categories which are relevant to North American Subaru owners, in order from lowest to highest HT/HS:

Resource Conserving 20 grade (Light Duty)
0w20 and 5w20 oils with API RC/ILSAC certification, may also Meet ACEA A1/B1 and OEM specifications. These oils have virgin HT/HS between 2.6 and 2.8.

Non-Resource Conserving 20 grade (Light Duty)
20, 0w20 and 5w20 oils which do not meet API RC/ILSAC specs, but may meet API S, and/or ACEA A1/B1. These oils have virgin HT/HS between 2.6 and 2.8.

Resource Conserving 30 grade (Light Duty)
0w30, 5w30, and 10w30 oils with API RC/ILSAC certification, may also meet ACEA A1/B1, A5/B5, C1 or C2. These oils have virgin HT/HS between 2.9 and 3.4.

Light Duty 30 grade (Non-Resource Conserving)
Any 30 grade oil which does not meet API RC/ILSAC requirements, but should meet API S when used in gasoline engines and may also meet ACEA A1/B1, A5/B5, C1 or C2. These oils have virgin HT/HS between 2.9 and 3.4.

Heavy Duty 30 grade
Any 30 grade oil with an unused HT/HS greater than 3.5. These oils cannot meet API RC/ILSAC requirements, but should meet API S when used in gasoline engines and may also meet ACEA A3/B3, A3/B4, C3, C4, E7 or E9.

40 grade (Heavy Duty)
All 40 grade oils are Heavy Duty and must have HT/HS greater than 3.5. Straight 40 grade and 15w40 oils are required by SAE J300 to exceed 3.7. Many high quality 0w40, 5w40 and 10w40 oils exceed 3.7 as well. Any 40 grade oil used in a gasoline engine should carry API S and/or ACEA A/B or C certification.

Low-SAPS engine oils
These oils are found in any commonly available viscosity grade from 0w20 up to 5w40, they can be Light Duty or Heavy Duty, their defining characteristic is low levels of Sulphated Ash, Phosphorous and Sulfur (SAPS). Other than generally requiring shorter oil change intervals, these oils perform equally to their higher-SAPS counterparts. ACEA C-series oils are the most common Low(est)-SAPS oils, but many oils are described by their formulators as Low-SAPS even without an ACEA C designation. With the exception of Sulphated Ash, API Resource Conserving and ILSAC oils contain similar levels of Phosphorous and Sulfur, and can usually be considered “Low-SAPS” even though they're not normally referred to as such.

Industry professionals and enthusiasts have noted that Low-SAPS oils tend to reduce intake valve deposits on direct injected engines, which may make these oils interesting to owners of newer, direct injected Subarus.

http://www.lubrizol.com/EngineOilAdd.../LowerSAPS.pdf

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7. How Oils are Marketed
It would be nice if formulators would label their oils with straightforward categories on the front label, but they don't. They use nebulous marketing terms like “synthetic” and “high-mileage”. Nevertheless, we can gain some useful information from the way oils are marketed.

Conventional Oils
Usually composed mostly of Group I and II base stock, but may contain substantial amounts of Group III, any presence of Group IV and V is as an additive. These oils are the bottom of each formulator's range and are thus produced to a price point. They are usually not labeled as “conventional”, that is implied by the lack of terms like “blend” or “synthetic”. They don't generally meet the toughest requirements of ACEA standards, but do meet some OEM standards. They tend to have lower TBN values and thus require shorter change intervals than synthetic or blend oils, but in many non-demanding applications they can provide excellent service for the life of the car. Conventional oils can be Light Duty, Heavy Duty, or Low-SAPS, though Low-SAPS conventional oils are rare. Being the “value” level in a formulator's product range, one can assume the additive packages are designed to meet the minimum requirements of the specifications as cheaply as possible.

Synthetic Oils
Composed of Group III-V base stocks. These oils occupy the upper range of formulator's product lines. Most moderately priced synthetics today are Group III base stock, but high quality Group III performs on-par or better than more expensive base stocks for all but the most demanding applications. They often have high TBN levels, but not always. The long-term shear and oxidation stability of synthetic base stocks is necessary but not sufficient for very long change intervals (10,000+ mi). There are many synthetic oils formulated with the very best base stocks which for various reasons are not formulated for long drain intervals. These oils tend to be race, street/track or Low-SAPS oils. Being the more expensive oils in a product line it can be assumed these oils get the best additives in addition to superior base stocks. Synthetic oils are available as Light Duty, Heavy Duty and low-SAPS varieties.

Formulators often have several tiers of synthetic oil. Shell Oil Products has Quaker State Ultimate Durability, Pennzoil Platinum, and Pennzoil Ultra Platinum in that order. Mobil has Mobil Super Synthetic and Mobil 1, Castrol has Edge and Edge Extended Performance. Upper tier oils tend to meet more stringent ACEA specifications. Some upper tier oils are long-drain oils which don't necessarily perform better at short intervals than their short-drain counterparts. Unless you're aiming for oil change intervals longer than 10,000 miles there's no reason to use Mobil 1 Extended Performance over “regular” Mobil 1 for instance. Since many late model Subaru owners will be choosing these oils, we'll detail some of the major players later.

Long-Drain Oils
These oils are marketed specifically as having the ability to do extremely long drain intervals. They are also always marketed as synthetics. Common examples are Amsoil Signature Series, Mobil 1 Extended Performance, and Castrol Edge Extended. They are marketed as being capable of drain intervals of 15,000 miles or more. It's important to note that many oils not specifically marketed as long drain oils are never the less capable of very long drain intervals, particularly those conforming to ACEA A5/B5, A3/B4, E7, and E9.

Synthetic Blend Oils
These oils are marketed by formulators as a blend of synthetic and conventional base stocks. Typically a blend of Group II and Group III, but there's no standardization for how much of each. One can generally assume that the additive package in these oils falls between synthetics and conventional oils. Whether blend oils are a good value is up for debate. Blends are available as Light Duty, Heavy Duty and Low-SAPS varieties.

High Mileage Oils
High mileage oils are marketed as synthetics, blends, and conventional oils. Their defining characteristic is higher levels of detergents and seal conditioners than conventional oils. Some have higher levels of anti-wear additives, often too high to conform to the latest API/ILSAC specs. Some meet API/ILSAC fuel economy requirements, some don't. The stated purpose of these oils according to formulators is to clean out sludge from neglected engines and to soften and revitalize aged seals, thus reducing leakage. Their additional anti-wear additives probably indicates higher levels of wear performance than conventional oils, but it is unlikely they outperform top-tear synthetics in that regard. Detergent effectiveness is also unlikely to be better than top-tier synthetics. High mileage oils tend to be a bit thicker than their “low-mileage” counterparts, often pushing the upper limit of their viscosity grade. It is generally safe to use these oils in new engines as long as the other specs are appropriate.

Racing Oils
Many national brands produce a lineup of oils labeled as “racing” oils, these include Red Line's racing series, Mobil 1 Racing and Amsoil Dominator. These oils have low levels of detergents and TBN which make them unsuitable for use in street cars. They are designed purely for racing applications where a “long” race is 500 miles and the engine never has a cold start. Many owners are attracted by the high levels of anti-wear, anti-oxidant and friction modification additives in these oils and erroneously presume them to be “better” for their modified street car. Unless your car is a bona fide trailered-to-the-track race car, DON'T DO IT. The additive packages of these oils are designed for the short drain intervals and narrow operating environment of racing, use in a street car can lead to deposits and other problems.

Street/Track Oils
These oils are designed for use in street cars which see heavy track day use. They maintain some levels of detergent additives and TBN for use on the street but shift their focus as much as possible toward track use. They may be appropriate for heavy use in a street car, but are generally expensive and unnecessary. Examples include Red Line (regular series), Valvoline VR1 and Motul 300V.

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8. Oil analysis – Closing the Loop
Where the manufacturers data sheets contain “typical” values for a particular type of oil when new, used oil analysis (UOA) measures many of those factors after it’s been in use for some time. UOAs are accomplished by taking a sample of oil from your engine, and sending it to a laboratory who offers the service. Particularly retentive enthusiasts will also send an unused sample of their oil for analysis so they can have baseline values for their particular batch of oil rather than the “typical” values listed on the product data sheet, this is known as Virgin Oil Analysis (VOA).

Companies offering UOA services include:
Blackstone Labs (http://www.blackstone-labs.com/)
Polaris Labs/Oil Analizers (http://polarislabs1.com/ or oiatesting.com)
Bently Tribology Services (http://www.cashmanequipment.com/bently/index.php)
Dyson Analysis (http://www.dysonanalysis.com/home.html)
Predictive Maintenance Services (http://www.theoillab.com/)
Wearcheck (also in Canada) (https://wearcheck.com/)
ALS Tribology (http://www.alsglobal.com/Our-Service...-Analysis.aspx)

Oil analysis was originally developed for over-the-road trucks which take several gallons of oil and can have large variance in oil change interval depending on if they're doing city deliveries or long hauls. In that context, it makes sense to spend $20 on analysis to determine if you need to replace $100 worth of oil, and UOA is well suited to this purpose. In a street car which only takes $25 worth of oil, we're generally not using UOA to minimize maintenance costs, we're using it to optimize oil choice, and for this purpose it is less well suited. For Subaru enthusiasts UOA is useful in a few ways, in decreasing order we can:

1. Confirm that the oil's virgin characteristics hold through the change interval.
UOA will measure the oil's KV100 which we can compare to the virgin value. Most baseline UOA packages don't measure the KV40, but labs will measure this for an additional fee. With both KV100 and KV40 we can calculate the used oil's viscosity index. Care should be taken though as the accuracy of the measurements is poor, and the calculated VI can vary wildly as a result.

2. Confirm that the change interval is appropriate for the car's operating conditions.
UOA will usually measure the TBN (sometimes it's an extra charge), and sometimes the Total Acid Number (TAN), Oxidation, and Nitration of the used oil. The exact condemnation limits for these parameters is a topic of debate, but following the guidance of your analysis lab will generally tell you if your change interval is appropriate for your operating conditions.

3. Have some idea that the engine is healthy.
Small amounts of metals including iron and aluminum become entrained in the oil as the engine wears, sudden spikes in some metals, or concentrations wildly outside the norm can indicate problems. The presence of other substances like fuel and coolant can also indicate problems. Care should be taken not to over-interpret these indicators as variances in usage can cause substantial variation in observed values without indicating a problem.

4. Satisfy some of our curiosity about the oil's additive package.
Lots of “internet tribologists” love to look at the additive elements which show up in UOA and proclaim one oil as “better” than another. This is folly as the UOA methods show only elements, not the compounds which make them up and also don't show all the potential elements. A UOA can tell us the concentration of molybdenum in the oil, but it can't tell us if that moly is tri-nuclear moly-DTC or moly-disulfide, two compounds which behave differently. Still, looking at these elements can sometimes be useful. For example, some oils use silicon compounds as anti-foaming agents. If you know you're using such an oil, the presence appropriate concentrations of silicon in UOA doesn't indicate poor air filtration.

This guide will not go into detail on how to interpret a UOA report because the labs who offer UOA explain it well on their websites. What we will cover is a basic overview of UOA, along with some of its limitations which are often not so clear. The information in the typical UOA report falls into four categories: elements present, physical properties, chemical properties, and contaminants present.

8.1 Elements
Elements are measured in parts per million and represent just what the name implies, chemical elements dissolved or suspended in the oil. They have three sources, the virgin oil, the engine itself, and the air and fuel flowing through the engine. It’s important to note that the report tells you nothing about what form these elements are present in, it measures only fundamental chemical elements, not molecules. Because of this we can only speculate as to the reason for their presence. For some elements this is straightforward, but others present problems. Elements commonly misinterpreted in UOA:

Iron
Iron comes from wear of iron or steel engine parts, iron compounds are not used in oil additives and are not present in air or fuel. The detection methods used in UOA only measure a narrow range of particle sizes for iron, so it's impossible to say whether small variations in iron concentration actually represent differences in oil wear performance. Iron concentration tracks with drain interval, so we can expect to see more iron in a 7,000 mile sample than in a 3,000 mile sample. Typical concentrations in Subaru engines vary from 10 ppm at short change intervals up to about 20 ppm for heavy use and long intervals.

Aluminum
Aluminum comes from wear of aluminum engine parts, particularly piston skirts, but sometimes journal bearings. Small amounts should be of no concern, but large amounts (over about 15 ppm in Subaru engines) may indicate poor air filtration, especially if accompanied by elevated levels of silicon (from ingested sand).

Silicon
Silicon has several potential sources. Anti-foaming additives in the oil and RTV sealant used to assemble or service the engine are benign, small particles of sand ingested through a poor quality or damaged air filter will increase wear. If an oil formulation is known to contain silicon, or if the engine is new or had a gasket replaced recently, the presence of elevated silicon should be of no concern. If neither of those explanation holds, and especially if aluminum is elevated (indicating piston wear) poor air filtration should be suspected. Some silicon from tiny ingested dirt particles is to be expected, and increases with change interval mileage. For typical change intervals and OEM air filtration, silicon typically shows 10-20 ppm in Subaru engines.

8.2 Physical Properties

KV100
KV100 is possibly the most important parameter to Subaru enthusiasts measured by UOA. It helps us know if the oil we selected based on its virgin properties actually retains those properties in service. Ideally the lab would measure HT/HS, and many offer that as an add-on service costing hundreds of dollars, but that's obviously cost prohibitive, so we use KV100 as a proxy. Luckily, automotive engineers have studied the relationship between KV100 and HT/HS, and it's relatively predictable. HT/HS is generally reduced by half the amount that KV100 is reduced due to shearing. So, an oil who's KV100 shears 12% in service will see its HT/HS reduced by 6%.

In practice most Group III synthetic oils shear 10-15% in use, Ester/PAO oils somewhat less, conventional oils somewhat more. If your oil shears more than this or if your usage results in thinner oil through fuel dilution, a thicker oil or one more resistant to fuel dilution is a wise choice.

http://www.astmtmc.cmu.edu/docs/dies...52501ATT12.PDF

Flashpoint
Oil's flashpoint is reduced primarily by the presence of fuel, but can also be reduced through shearing and other mechanisms.

8.3 Chemical Properties

TBN
This is the oil's remaining ability to neutralize acidic contaminants, and is the primary determinant of whether the change interval can be extended. Different labs recommend different minimum limits for TBN. The most popular lab, Blackstone, recommends 1.0, second most popular Polaris/OAI, recommends 2.0. Newer additive packages exhibit non-linear depletion of TBN which older formulations did not. This is particuarly true for low-SAPS oils which often start with a seemingly low TBN under 7.0, but can usually handle moderately long change intervals any way.

8.4 Contaminants

Fuel
The presence of fuel in oil will lower the flashpoint and viscosity through damage to base stocks and additives, substantially shortening the oil's service life. Properly sampling the oil after heating it thoroughly should remove short term cold-start fuel from the oil but many engines regularly run rich and substantial fuel dilution over the long term can be the result. Labs use various methods to estimate fuel content, Blackstone in particular estimates it using flashpoint which can lead to large variances in the reading.

Water
The presence of water in oil is often an indication of poor sampling procedure. The oil sample should be taken after the car has been warm sufficiently long for all water in the oil to be boiled off. Substantial water content in a sample taken hot might indicate a mechanical problem with the engine.

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9 Selecting an Oil for your Subaru

After all that we finally come to the meat of this guide. In basic terms, we'll start with the recommendations in the owners manual, reverse engineer and read between the lines a bit, and then use that informed speculation to modify the recommendations based on our unique operating conditions.

To this point you will notice that the specifications governing engine oil focus on typical conditions (KV100) or worst case conditions (MRV, HT/HS), but don't say much about actual operating conditions. Since the specifications are written for cars in general, not those of a particular manufacturer let alone a particular usage scenario, this is understandable. So now it's time to think about the actual operating conditions inside our engines, and ask ourselves what Subaru intended.

9.1 Subaru Oil Requirements

The oils most prominently recommended by Subaru for normal use in various engines are:
EJ series naturally aspirated – API RC/ILSAC 5w30
EJ series turbo – API RC/ILSAC 5w30 (synthetic from 2011)
FB series naturally aspirated – API RC/ILSAC 0w20
FA series naturally aspirated – API RC/ILSAC 0w20
FA series turbo – API RC/ILSAC 5w30

Prior to 2011 Subaru owner's manuals contained specific recommendations up to 50 grade for heavy use in high temperatures, they continue to contain vague language about heavier oil for high temperatures, but no specific grades or temperatures are mentioned. Why have they removed reference to heavier grade oils? We we don't know for sure, but we can speculate fairly effectively. Subaru's recommendations place higher emphasis on fuel economy and emissions system durability than an owner might. In order to use API RC oil in the EPA fuel-economy tests, the EPA requires manufacturers to either list it as the only grade in the owner's manual or to list it as the “preferred” grade. Subaru used to list API RC oils as “preferred”, but now mentions them exclusively. The other reason to emphasize API RC oil is emissions system durability. Subaru is required by law to cover important emissions system components for at least 80,000 miles (150,000 on PZEV models), this applies even if the vehicle burns oil. API RC oils have lower levels of potentially harmful additives which “poison” emissions equipment when burned. Combine those two regulatory requirements and we have a pretty good idea why the recommendations for high viscosity oils with robust additive packages went away. Is Subaru screwing owners over? Generally no, Subaru doesn't like warranty claims any more than owners do, so in most circumstances the recommendations provide excellent service in normal operation, the one possible exception is the turbo EJ engine (see below).

epa.gov/obd/pubs/420f09048.pdf

Extrapolating from Subaru's recommendations
So, Subaru makes recommendations for “normal” use, but what are your usage conditions? How are they different from Subaru's baseline? How do those conditions affect oil choice? Answering those questions will require some informed speculation and will leave substantial ambiguity. If you're towing a trailer into the mountains of Denali National Park in January or track driving at Road Atlanta in the summer, the “best” oil is likely different from what's in the manual. Ideally, we could measure oil temperature under various conditions to inform our choice, but until now most Subarus were not equipped with oil temperature sensors, and most owners didn't invest in aftermarket ones. Luckily, newer FA series engines (FB too?) are equipped with an oil temperature sensor which can be read using a scan tool, owners of such cars who are truly interested can monitor their oil temperatures and make a more informed choice. Most owners though will have to make due with generalizations about how the car is used.

What can we assume about how Subaru designed the hydrodynamic interfaces of the engine? Well, we can assume they used the Stribeck curve, remember that? Remember point 'a' the transition between mixed-film and hydrodynamic lubrication which happens at a certain viscosity? Notice how the friction increases quickly as we move into mixed-film lubrication and much more slowly as we move farther into the hydrodynamic regime? Being mixed-film lubrication, increased friction also indicates increased wear, while increased friction in the hydrodynamic regime reflects only increased hydrodynamic drag without increased wear. It is therefore much preferred to stay in the hydrodynamic regime even if it means slightly increased friction, and Subaru's engineers know that. We can therefore assume that Subaru designed the engine so under “worst-case” conditions the operating point of the engine will be at point 'a' and all other times will be to the right. We can further assume that this condition will be at maximum oil temperature, which in terms of piston cooling will be sub-optimal. The engine will be designed to survive these conditions, but not thrive under them. This is a simplistic, but instructive view.


Figure 7 – The Stribeck Curve
1 – Boundary lubrication
2 – Mixed film lubrication
3 – Hydrodynamic lubrication

So what exactly is “worst-case” operation? Subaru has given us some clues in the owners manuals by indicating that thicker oils are recommended for heavy use and high temperatures. From that clue we can infer that the viscosity of the oil recommended for the car at the temperatures seen during moderately heavy street use puts us a bit to the right of point 'a' on the Stribeck curve, for a little bit of safety margin. Such use would be twisty-road carving on a hot day (say 90° F) in a car that is not heavily loaded and not climbing a mountain. Any decrease in viscosity, either through shearing or higher oil temperatures, risks using up the safety margin and moving toward mixed-film lubrication.

In reality it's not quite as bad as it seems. Notice the dashed line to the left of point 'a'? That's the actual friction curve of real motor oil. The idealized Stribeck curve is for a pure hydrodynamic lubricant, one without anti-wear or friction modification additives, an actual oil will not see the large increase in friction in the transition to mixed-film lubrication because it contains anti-wear and friction modification additives. So a small amount of mixed-film operation will not result in bearing death, but being diligent owners we want to avoid the situation any way.

So, if you use your car only moderately hard, the oil recommended in the owner's manual should provide good service, but the definition of “moderately hard” is ambiguous, and the consequences of poor selection are asymmetric; an oil which is too thick costs you a little fuel economy and a couple horsepower, an oil which is too thin causes bearing wear or possibly a spun bearing. Given that, selecting an oil which is slightly thicker than we really need is entirely rational in pursuit of a bit of safety margin, but there's a problem.

At the same temperature, a thicker oil will provide a stronger hydrodynamic film, but it will also run hotter under the same operating conditions. The additional work done by the engine to move the thicker oil and spin rotating parts through it ends up as heat in the oil. A 40 grade oil won't run so much hotter that it's operating viscosity is lower than a 30 grade, but we can't simply compare KV100 values and assume they represent operating viscosity. There's a delicate balancing act here, oil that's too thin risks bearing wear, oil that's to thick promotes detonation by keeping the pistons hotter.

That means the range of optimum oil temperature is quite narrow, while the range of acceptable oil temperature is much wider. To keep water and fuel out of the oil we want the oil temperature above 212°F (the boiling point of water), but we want the pistons as cool as possible, so optimum oil temperature is in the range of 215-230°F. Operating temperatures down to 170°F or so occur in low load running in cold weather and generally aren't a problem. Temperatures up to 270°F occur in heavy use in high temperatures and usually aren't a problem either. This thread from FT86 club takes advantage of the oil temperature sensor in the 86 twins to give us some decent information on typical oil temperatures: http://www.ft86club.com/forums/showthread.php?t=29965

Taken together, these factors indicate that wise oil selection will be at most two categories thicker than recommended by Subaru. For engines which recommend 0w20, a HD 30 grade is about the thickest wise choice, for 5w30 engines, a 40 grade is about the thickest wise choice. 40 grade oil in a 0w20 car or 50 grade in a 5w30 car could be used in the event of infrequent very heavy use, but is definitely sub-optimal. An examination of viscosity-temperature behavior will show us why.

Here's a viscosity chart with typical oils from the relevant categories zoomed in on the normal operating temperature range. We can see that stepping up one category results in an oil which has the same viscosity about 20°F (~10°C) warmer.


Figure 8 – Operating Temperature Viscosities

If Subaru recommends 0w20 for your engine, the bearings should be very happy with 7.5 cSt oil, if we put RC 5w30 into the engine, the oil temperature can rise to 240°F before the oil viscosity drops below 7.5 cSt, now we're at the upper limit of optimal oil temperature. With HD 5w30 the 7.5 cSt temperature rises to 260°F, basically the upper limit of acceptable. In other words, using a 40 grade oil implies we will be operating the engine at unacceptably high oil temperatures. And since using a heavier oil encourages higher operating temperatures, we're compounding the problem. So, if you think you need 5w40 in your car that calls for 0w20, what you really need is an oil cooler, possibly a big one.

The same logic goes for a car that calls for 5w30, the bearings should be very happy with oil at 10 cSt, stepping all the way up to 50 grade implies oil temperatures in excess of 260 °F, well outside the optimal range. So why did Subaru formerly recommend up to 50 grade oils for heavy use and high temperatures? Simple, it's a band-aid for the small fraction of owners who use their cars that heavily. Subaru's choice was either add an oil cooler to every car they made, which costs them money, or put the heavy oil recommendations in the manual, which costs them nothing.

The above chart is viscosity for new oil, but what about used oil? The lines in the chart simply move down as the oil shears, but they retain their shape. Since we don't know Subaru's exact design point any way, the conclusions about oil choice hold whether we're looking at a graph of used oil or new.

We've talked a lot about viscosity here, but what about other requirements? The API/ILSAC specs called for by Subaru ensure acceptable performance in areas like compatibility with seals, detergency, and TBN. Note that many oils, especially top-tier synthetics, exceed the minimum requirements by a substantial margin, and can therefore be expected to handle substantially longer change intervals or more severe service than the minimum-spec oils Subaru must assume when making recommendations.

9.2 Usage Scenarios
Let's take a moment to categorize use scenarios. Your use scenario is the worst case you will encounter during a particular oil change interval.

Normal Street Driving
Just like it sounds, commuting, highway trips, etc. Even the occasional fast blast down a twisty road qualifies as normal street use with an unmodified car. You simply can't apply full throttle long enough on the street to raise the oil temperature high enough for it to qualify as heavy use which might require thicker oil. An owner who lives in a particularly warm climate (e.g. Phoenix, AZ) might consider hard driving on a twisty road as heavy use. High proportions of city driving can be cause for shortened oil change intervals, but normal street driving generally allows normal change intervals as recommended by Subaru, or even longer if confirmed by UOA.

Heavy Use – Trailer Towing and Track Driving
Heavy use involves long periods of operation under heavy load, either due to high speeds on the track or heavy weight and/or steep grades on the road. Heavy use combined with high ambient temperatures could be considered “extra heavy”. The result is higher oil temperatures and consequently thinner oil. If you use your car in this way, stepping up to the next higher category and/or grade of oil is wise, at the very least select an oil within the lower category which displays the highest shear and thermal stability. Owners who regularly use their cars heavily should consider an oil cooler, especially if the car did not come equipped with one from the factory.

Track driving also subjects the engine to high g-loads which can cause large amounts of oil to be ingested through the PCV system, potentially encouraging knock. Autocross is a unique situation, the duration of heavy load is generally not enough to result in high oil temperatures, but the g-loading can cause the engine to ingest oil through the PCV. Owners who regularly track and/or autocross may consider adding an air-oil separator to the engine to minimize oil ingestion, or at least using a street/track oil designed to minimize negative effects when ingested.

Heavy use often necessitates shorter oil change intervals due to fuel dilution, thermal stress, and shearing.

Extreme Cold
With the easy availability and low cost of modern synthetic oils, few compromises in oil performance are required to handle occasional temperatures down to -22°F, the limit of a 5wXX multi-grade oil, but for extremely cold temperatures a 0w multi-grade oil is wise. For our purposes, extreme cold is frequent temperatures below -13°F. Remember the definition of the w number grades, 10w oils are good down to -13°F (-25°C), 5w oils are good down to -22°F (-30°C) and 0w oils are good down to -31°F (-35°C). There are some benefits to using an oil one grade better than the temperatures you'll encounter, so 5w oils will show small benefit over 10w oils up to about -4°F, and 0w oils will show small benefit over 5w oils up to about -13°F. Few places in the lower 48 states see any benefit from 0w oils, but they can occasionally be useful in states bordering Canada. Canadian and Alaskan owners are wise to use 0w oils during the winter months.

Extreme cold can shorten optimum oil change intervals, especially if the car is used for short trips where the oil never reaches optimum temperature.

Modifications
Modifications can run the gamut from simple cat-back exhausts, to custom built engines with giant turbos, making generalization about oil in modified engines difficult. Almost without exception modifications which increase horsepower will also increase oil temperatures, making thicker oil necessary in modified cars when it wouldn't be in unmodified cars. Owners of modified cars who intend to use them heavily are wise to add a high capacity aftermarket oil cooler, even if the car was equipped with one from the factory. Doing so will of course keep oil temperatures down, but will also keep the pistons cooler, which helps prevent knock. Modified cars are often tuned to run rich, which can increase fuel dilution and shorten optimum change intervals.

Last edited by gpshumway; 04-07-2015 at 08:02 PM.
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Old 04-07-2015, 06:24 PM   #10
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9.3 Recommendations for specific cars/engines

9.3.1 EJ series Naturally Aspirated Engines
In North America, all Subaru four cylinder engines from 1991 until 2011 were variants of the EJ series. Those without forced induction are not demanding of oil and will generally function well on the Light Duty 5w30 oils recommended by Subaru. Naturally aspirated EJ engines were discontinued at the end of the 2011 model year in the Impreza but were produced through 2012 in the Legacy/Outback.

Street driving
Light Duty 30 grade conventional or synthetic, 5w30 is most common but 0w30 and 10w30 will also perform well in appropriate temperatures. Owner's manuals call for Resource Conserving/ILSAC 5w30. Conventional oils perform fine at moderate change intervals up to 5,000 miles, synthetics can be used to 10,000 miles or more, but should be confirmed with used oil analysis. Extending change intervals beyond the OEM recommendations could risk warranty coverage.

Heavy Use
At a minimum a 30 grade Light Duty synthetic is a wise choice. If you don't expect to see temperatures below 0°F, 10w30 synthetic oil is often more shear stable and resistant to heat than other Light Duty oils and can provide a small safety margin for heavy use. For very heavy use like uphill trailer towing or track driving in high temperatures, a Heavy Duty 30 grade or 40 grade oil is wise.

Modified Engines
Normal bolt-on modifications combined with a near-OEM redline should not necessitate altering the oil choice otherwise made for operating conditions. API RC/ILSAC 5w30 for the street and slightly heavier oil for heavy use should still be adequate. Aftermarket forced induction systems have the potential to make the engine very demanding on oil as do “race-built” naturally aspirated engines. In such a case, consult with your engine builder, or at the very least follow recommendations for a modified turbo EJ engine (below).

Extreme Cold

A Light Duty 0w30 synthetic oil should be sufficient for a naturally aspirated EJ engine in extreme cold, even if used heavily, no need to use a thicker HD oil.

9.3.2 Turbocharged EJ Series Engines
Subaru introduced the turbo EJ engine in the 1991 Legacy turbo, and began selling them in volume with the 2002 WRX. The engine's lone remaining application is in the 2015+ WRX STI. This engine is the most problematic Subaru engine for oil selection because of the sub-optimal recommendations made by Subaru (particularly after 2010) combined with aggressive tuning of the engines for fuel economy and emissions. A full explanation of the issues is beyond this guide, but the primary issue is spun bearings due to contact between the crankshaft and the bearing (lubrication failure) the proximate cause is detonation which can be worsened by oil ingested through the PCV. Additionally oil which is thin either because it's very hot or because of poor shear stability is less capable of protecting the bearings. It is therefore reasonable to use a thicker oil in a turbo EJ to reduce, but not eliminate, the chance of a spun bearing.

Street Driving
The Resource Conserving 5w30 recommended in the owner's manual (synthetic from 2011) is just barely adequate for street driving, especially in the 2008-2014 WRX which does not have an oil cooler. A quality, shear-stable RC 30 grade synthetic conforming to ACEA A5/B5 specifications is recommended as a minimum. Heavy Duty 30 and 40 grade oils are a reasonable upgrade.

Heavy Use
Turbo EJ owners who use their car heavily are wise to use a HD 30 grade oil at a minimum, and HD 40 grade oils can provide additional safety margin. Installation of an oil cooler in cars not so equipped from the factory is wise for heavy use, a high capacity aftermarket cooler can provide additional safety margin.

Modified Engines
Owners of modified cars are wise to use Heavy Duty 30 grade oil at a minimum for street use. Modified cars receiving heavy use should have an oil cooler installed in addition to the use of HD oil. For occasional heavy use, modified cars can get away with shear stable HD 40 grade or 50 grade oil conforming to ACEA A3/B4, or a combination of E7 or E9 and a gasoline specification like API SM.

9.3.3 Naturally Aspirated FB Series Engines
With the exception of the BRZ sports car, all naturally aspirated Subaru four cylinder engines since 2013 are of the FB series, it has replaced the EJ series as Subaru's main naturally aspirated engine. The FB25 was introduced to North America in the 2011 Forester, the FB20 followed in the 2012 Impreza, and in 2013 the FB25 replaced the EJ25 in the Legacy/Outback. All versions of this engine recommend 0w20 synthetic oil in all operating conditions in North America. Generally, performance with such oil has been good, but many owners of early cars have reported high oil consumption. Some engines were subject to a manufacturing defect where the gaps between piston rings lined up and fostered excessive oil consumption. Other engines seem to consume substantial oil, but not enough to indicate they have the piston ring defect. Subaru has revised their definition of excessive oil consumption to be more than a quart every 600 miles (previously a quart every 1,000 miles), which strikes many owners as ludicrously excessive. Those owners may choose to use thicker oil simply to reduce the consumption.

Normal Street Driving
Synthetic API RC/ILSAC 0w20 has proven suitable for FB engines on the street. Top-tier national brands and long drain versions can be extended well beyond the factory recommended 6,000 mile change interval. (7500 mi for 2011-2014) Such use is not wise during warranty, and should be accompanied by UOA.

Heavy Use
Subaru of America (SOA) does not specify heavier oil for heavy use in the FB engines, but stepping up to an API RC/ILSAC 30 grade oil for heavy use will provide some margin of safety. Doing so poses some risk of denial of a warranty claim.

Modified Engines
Normal bolt-on modifications should not alter the oil recommendations for normal or heavy use. Modified FB series engines are rare at the time of writing, so feedback on them is minimal, choose with caution.

Naturally Aspirated, Direct Injected FA Series Engines
The FA20 is used only in the BRZ sports car (and its Scion FRS twin), it is similar to the FB20 but has direct injection and a higher redline, both of which indicate it might be a bit harder on oil. The FA20 shares its D4-S fuel injection system with some Lexus models and has both direct and port fuel injectors. Judging by Lexus experience this engine is less likely to show fuel dilution and intake valve deposits than many direct injected engines. Still more prone to fuel dilution than port injected naturally aspirated engines.

Normal Street Driving
Synthetic API RC/ILSAC 0w20 has proven suitable for FA20 engines on the street. Extension of drain intervals past the factory recommended 6,000 miles is possible, but use caution as the direct injection system can sometimes show fuel dilution that the port-injected FB series does not experience. Subaru allowed 7,500 mi change intervals in the FA20 during the 2013 and 2014 model years, then shortened the recommendations to 6,000 mi for 2015. Use of UOA is wise if extending intervals.

Heavy Use
Subaru recommends heavier oil of an unspecified grade for heavy use in FA engines, Stepping up to an API RC/ILSAC 30 grade oil for heavy use will provide some margin of safety. If ambient temperatures are above 0°F, use of a quality API RC/ILSAC 10w30 synthetic should be sufficient for heavy use.

Modified Engines
Normal bolt-on modifications combined with a near-OEM redline should not necessitate altering the oil choice otherwise made for operating conditions. API RC/ILSAC 0w20 for the street and slightly heavier oil for heavy use should be adequate. Aftermarket forced induction systems have the potential to make the engine very demanding on oil as do “race-built” naturally aspirated engines. In such a case, consult with your engine builder, or at the very least follow recommendations for a modified turbo FA engine (below).

9.3.4 Turbocharged, Direct Injected FA series Engines
The FA20 DIT was introduced in the 2014 Forester XT and replaced the EJ25 in the 2015 WRX. Direct injection is new to Subaru and carries with it a couple potential problems highlighted by other manufacturers, namely fuel dilution of the oil and carbon deposits on intake valves. Early UOA results in FA20 DIT engines indicate fuel dilution is a substantial problem, and Subaru's shortening of the change interval from 7,500 to 6,000 miles for 2015 provides some evidence they're aware of the problem. No reports of carbon buildup have surfaced as of the time of writing, but it is a problem owners should watch. The engines are still fairly new, but the incidence of spun bearings in the FA turbo engines appears substantially less than their EJ series forbears, so the necessity of using thicker oil in these engines seems less than in the EJ. The FA20 DIT already uses a thicker oil than its naturally aspirated brother, the FA20 (5w30 vs 0w20). The potential for carbon deposits, though may make a low-SAPS European oil (ACEA C3 or C4) a good choice, with the extra HT/HS safety margin coming as a bonus.

Normal Street Driving
Synthetic API RC/ILSAC 5w30 has proven suitable for FA turbo engines on the street.

Heavy Use
Subaru does not specify heavier oil for heavy use in the FA20 DIT, but stepping up to a Heavy Duty 30 grade or 40 grade oil for heavy use will provide some margin of safety. Doing so poses some risk of denial of a warranty claim.

Modified Engines
Owners of modified cars are wise to use HD 30 grade oils at a minimum for street use. Modified cars receiving heavy use should have a high capacity oil cooler installed in addition to the use of HD oil. For occasional heavy use, modified cars can get away with shear stable HD 40 grade oil conforming to ACEA A3/B4, or a combination of E7 or E9 and a gasoline specification like API SM.

9.4 Subaru Oil Requirements – Warranty Redux
A lot of discussion on the forum centers around what oil is required to maintain warranty coverage. The reason for so much debate about warranty requirements is Subaru’s confusing and often self-contradictory recommendations in the owner’s manual, which are often just that – recommendations without clear requirements. Generally between 2002 and 2010 Subaru recommended conventional API RC/ILSAC 5w30 oil. During this period the manuals also mention thicker grades for hot weather and heavy use. In 2011 the recommendations changed substantially with the introduction of 0w20 oil for the FB engine and the removal of specific grades heavier than 5w30 for the EJ engine. Since any Subaru older than 2009 is beyond the 5yr/60k powertrain warranty, we will ignore the older manual recommendations. Owners of older cars (or newer cars with more miles) can select oil based purely on technical properties without regard for Subaru’s warranty requirements.

Prior to the synthetic recommendations, the 2009-2010 Impreza manual is typical. The recommendations are the same for both turbo and naturally aspirated cars.


Figure 9 – 2010 Owner's Manual Oil Recoommendations
http://techinfo.subaru.com/search/index.html

Page 11-12 recommends oils which conform to API SM + Resource Conserving, or ILSAC GF-4, and shows a table which includes 5w40 grade oil for any temperature. Great, but 5w40 cannot be Resource Conserving or ILSAC GF-4, the best you can do in a 5w40 grade oil is plain API SM. The next page makes recommendations for severe driving conditions which require only API SM or SL, but fails to mention 5w40 as an acceptable grade, listing only 30, 40, 10w50, 20w40 and 20w50! To pile stupidity on top of confusion, there’s no advice on what weather conditions the severe service grades are suitable for. You certainly wouldn’t want to use straight 40 grade at 0°F.

So, if I tow a trailer in a Minnesota winter (the author does), which oil should I be using? If I have an engine failure while using a 5w40 oil, will Subaru deny my warranty claim because the oil isn’t Resource Conserving? None of this is clear.

As bad as the 2009-2010 manual is, it at least has a chart allowing 5w40 oil. The 2011-2015 manuals start the oil section by advising you to use “Subaru approved” oil, but then tell you to contact your dealer to find out what that oil is. Brilliant. So my dealer, who’s dumber than a box of rocks, gets to decide which oil is approved? Presumably the only “approved” oil is one that comes in a Subaru bottle, at great expense. An alternate engine oil is apparently OK if the approved oil isn't available. The alternate oil is apparently synthetic 5w30, but then the manual contradicts itself in the very next sentence saying conventional 5w30 is OK if synthetic is unavailable. Huh??? How do we define available? Anything is available through the internet if we're willing to wait a week. The very next paragraph mentions using 5w40 conventional oil for replenishment only. NASIOC community members have looked hard for any 5w40 oil marketed as conventional and come up empty, and any way, what’s wrong with 5w40 synthetic? Why even mention the oil being conventional? That implies synthetic is somehow not acceptable. Well done, Subaru.

As bad as the EJ engine recommendations have become, the FB series engines really take the cake. They make the same “approved oil” pitch as the EJ manuals, give an alternate oil as synthetic 0w20, then allow a non-existant conventional 0w20, and finally recommend conventional 5w30 or 5w40 for replenishment, completely ignoring the more appropriate 5w20 conventional and synthetic options. Brilliant, Subaru, just brilliant. No wonder owners are confused.

The BRZ manual contains the lone remaining reference to heavy use. It says “An oil with a higher viscosity ... may be better suited if the vehicle is operated at high speeds, or under extreme load conditions.” but doesn't give any guidance on what constitutes high speeds or extreme loads, nor does it detail exactly what “heavier oil” means. Do we use 30 grade? Or even 40? While the manual language frees the owner to use almost any oil in heavy use, a recalcitrant dealer can use the ambiguity as an excuse to deny warranty coverage and force the owner to seek redress in court. Courts are generally more expensive than engines, so few owners actually do this.

So what's the concerned owner to do? The strictest interpretation of the current owner's manual recommendations is to use “Subaru Approved” oil from the dealer. Those who lie awake at night terrified of a non-warrantied engine failure should simply have the dealer change the oil, confirm they're actually using the Subaru oil and save the receipts. There, wasn't that easy? Aren't you glad you spent all that time reading this guide? Owners who are this risk averse shouldn't be participating in any activities which Subaru could consider abuse, which is also grounds for denying warranty claims. That means no autocross and no track days.

One step up the risk ladder is using an oil from the exact same category as the Subaru brand oil. That means using an API RC/ILSAC synthetic oil in 0w20 or 5w30 grade depending on your engine. This strategy is very low risk, but only provides documentary protection against a denied warranty claim, the oil itself doesn't protect the engine any better than the Subaru oil during heavy use.

BRZ/FRS owners with less risk aversion who use their cars heavily can step up to a 30 grade oil under the “heavy use” recommendations in the manual, but 2011+ EJ owners are in a bit of a bind. Using a Heavy Duty 5w30 oil which meets API SM (or newer) is the lowest risk strategy, unfortunately such oils are rare and expensive. Currently all such oils are designed for European OEM applications and cost $10+ per quart, but for the semi-nervous owner they're the best choice. See oil recommendations below.

A note on modifications – if you've modified your car, you shouldn't be counting on warranty coverage any way, and you should select the oil which best suits your operating conditions regardless of Subaru's recommendations. That's the ethical thing to do, modding a car is a pay-to-play activity.

Last edited by gpshumway; 04-07-2015 at 08:35 PM.
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Old 04-07-2015, 06:25 PM   #11
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10 Favorite oils in various categories

While an effort has been made to ensure the information in this section is correct at the time of writing, oil makers change their formulations constantly, sometimes changing the category of an oil in the process. For instance, during a recent reformulation Valvoline Maxlife Full Synthetic 5w30 changed from being a Heavy Duty oil conforming to ACEA A3, to a Light Duty resource conserving oil conforming to ILSAC GF-5. Check current product data from the manufacturer if in doubt, links to product data have been included where available.

10.1 Light Duty 5w30 Conventional oils
All RC conventional oils from national brands perform similarly, there's no need to detail the small differences between them here. If you want better oil, spend a few bucks and buy a good blend or synthetic. Good blends like Valvoline Maxlife and Pennzoil Gold and lower tier synthetics like Quaker State Ultimate Durability are only slightly more expensive than conventional oils. If you must split hairs to differentiate between conventional oils, choose one meeting Ford M2C and/or GM dexos specs.

10.2 Resource Conserving 0w20 synthetic oils.

Pennzoil Platinum 0w20 – HT/HS ??
API SN +RC/ILSAC GF-5
Excellent oil from Shell Oil Products US (SOPUS), but no ACEA or dexos rating. SOPUS no longer publishes HT/HS for Pennzoil Platinum

Pennzoil Ultra Platinum 0w20 – HT/HS ??
API SN +RC/ILSAC GF-5, ACEA A1/B1, GM dexos1.
Excellent oil from Shell Oil Products US (SOPUS) Has ACEA A1/B1 and dexos, but also higher NOACK than Pennzoil Platinum, right on the ACEA limit of 13%. SOPUS no longer publishes HT/HS for Pennzoil Ultra Platinum.

Mobil 1 Advanced Fuel Economy 0w20 – HT/HS 2.7
API SN +RC/ILSAC GF-5, ACEA A1/B1, GM dexos1, Ford M2C.
Excellent oil from Exxon Mobil, the only 0w20 claiming adherence to Ford's WSS-M2C947-A spec for 5w20 oil, which implies it meets the stricter turbocharger deposit specifications (TEOST 33C) for 5w20. UOA has shown fairly poor shear stability for M1 AFE 0w20, however. As of 5/28/15 Mobil's web product page and PDS no longer list ACEA A1/B1 for AFE 0w20, indicating a possible recent formulation change.

Castrol Edge 0w20 – HT/HS ??
API SN +RC/ILSAC GF-5, ACEA A5/B5, OEM approvals
Excellent oil from BP. Latest version has titanium additive trickled down from older “Edge with Titanium FST” formulation (now called Edge Extended). Castrol doesn't publish real HT/HS or many other specs like MRV and CCS for their products, only spec minimums, which makes detailed evaluation hard.

Castrol Edge Extended 0w20 – HT/HS ??
API SN +RC/ILSAC GF-5, ACEA A5/B5, OEM approvals
Excellent oil from BP. Broadly similar to Mobil 1 Extended Performance. Guaranteed by Castrol for up to 15,000 miles. Now that the titanium additive package has trickled down to 'regular' Edge, there's little reason to use the 'Extended' version for change intervals of 10,000 miles or less. Castrol doesn't publish real HT/HS or many other specs like MRV and CCS for their products, only spec minimums, which makes detailed evaluation hard.

Subaru (Idemitsu) 0w20 – HT/HS ??
API SN +RC/ILSAC GF-5
The Subaru branded oil made by Idemitsu Lubricants of Japan. Generally similar to top-tier domestic brands like Pennzoil and Mobil 1. No ACEA rating, but for an oil marketed in the US as an OEM lubricant, that's hardly expected. Product data is hard to come by for this oil.

10.3 Resource Conserving Light Duty 30 grade Synthetic oils

Amsoil OE and XL series 5w30 – HT/HS 3.3
API SN +RC/ILSAC GF-5
The difference between the XL and OE series is their TBN, XL oils are designed for longer drain intervals, while OE oils are designed for OEM recommended change intervals. Other than TBN the base stocks and additive packages are the same. The 5w30 grade of these oils have some of the highest HT/HS viscosities within the RC 5w30 category, and are thus interesting to turbo Subaru owners highly concerned with warranty coverage, who wish to conform to the strictest interpretation of the owner's manual recommendations.

Amsoil Signature Series 5w30 – HT/HS 3.1
No Formal Certifications
Mentioned here only because it dos NOT carry API or ILSAC certification, and therefore could pose a risk to warranty coverage. Amsoil uses tricky “recommended for” language in their marketing which implies conformance to API and ILSAC standards, but Signature Series is not officially certified. It is excellent oil, but its claim to fame is very long drain intervals, similar to Mobil 1 Extended Performance and Castrol Edge Extended. Unless you're extending your drain intervals past 10,000 miles, there are better ways to spend $10+ per quart on motor oil.

Pennzoil Platinum 5w30 – HT/HS ??
API SN +RC/ILSAC GF-5, ACEA A5/B5, + OEM approvals
Excellent oil from SOPUS. Shell no longer publishes the HT/HS viscosity for Pennzoil Platinum.

Pennzoil Ultra Platinum 5w30 – HT/HS ??
API SN +RC/ILSAC GF-5, ACEA A5/B5, + OEM approvals
Generally similar to Pennzoil Platinum but with increased levels of cleaning additives and higher TBN, but also with higher NOACK. Shell no longer publishes the HT/HS viscosity for Pennzoil Ultra Platinum.

Mobil 1 5w30 – HT/HS 3.1
API SN +RC/ILSAC GF-5, ACEA A1/B1?, OEM approvals
Mobil 1 5w30 has a bit of a bad reputation on NASIOC because of the sub-par performance of the early API SM formulation, the latest API SN formulation performs as well as any ILSAC 5w30. ExxonMobil warrants Mobil1 for use up to 10,000 miles. As of 5/28/15 Mobil 1's web information page no longer lists any ACEA specs for M1 5w30 (non-EP) the PDS lists A1/B1, indicating a possible recent formulation change. Formerly M1 5w30 was ACEA A5/B5

Mobil 1 Extended Performance 5w30 – HT/HS 3.0
API SN +RC/ILSAC GF-5, ACEA A1/B1, OEM approvals
Generally similar to 'standard' Mobil 1 with slightly lower HT/HS. ExxonMobil warrants M1 EP for use up to 15,000 miles, but for change intervals less than 10,000 miles there is no reason to use M1 EP in place of 'standard' Mobil 1.

Castrol Edge 5w30– HT/HS ??
API SN +RC/ILSAC GF-5, ACEA A5/B5, OEM approvals
Excellent oil from BP. Latest version has titanium additive trickled down from older “Edge with Titanium FST” formulation (now called Edge Extended). Castrol doesn't publish real HT/HS or many other specs like MRV and CCS for their products, only spec minimums, which makes detailed evaluation hard.

Castrol Edge Extended 5w30– HT/HS ??
API SN +RC/ILSAC GF-5, ACEA A5/B5, OEM approvals
Excellent oil from BP. Broadly similar to Mobil 1 Extended Performance. Guaranteed by Castrol for up to 15,000 miles. Now that the titanium additive package has trickled down to 'regular' Edge, there's little reason to use the 'Extended' version for change intervals of 10,000 miles or less. Castrol doesn't publish real HT/HS or many other specs like MRV and CCS for their products, only spec minimums, which makes detailed evaluation hard.

Subaru (Idemitsu) 5w30 – HT/HS ??
API SN +RC/ILSAC GF-5
The Subaru branded oil made by Idemitsu Lubricants of Japan. Generally similar to top-tier domestic brands like Pennzoil and Mobil 1. No ACEA rating, but for an oil marketed in the US as an OEM lubricant, that's hardly expected. Product data is hard to come by for this oil, the MSDS linked above was posted by user “Toombs” in 2013 and may not be current.

Mobil 1 Advanced Fuel Economy 0w30 – HT/HS 3.0
API SN +RC/ILSAC GF-5, ACEA A5/B5, OEM approvals
The only ILSAC 0w30 oil readily available in the USA. Performance is generally similar to high quality 5w30 synthetic oils except at very low temperatures where M1 AFE excels. UOA has shown M1 AFE 0w30 to be more shear stable than its 0w20 sibling. Alaskan and Canadian owners of Subarus calling for 5w30, this is your winter oil. Canadian owners can also use the equivalent from Petro Canada which is generally less expensive. Because this oil is a different grade than called for in the owner's manual there is a slight chance of warranty issues when using it.

10.4 Light Duty 30 grade Synthetic oils (non Resource Conserving)

Mobil 1 High Mileage 5w30 – HT/HS 3.3
API SL, ACEA A5/B5
A high quality oil with high levels of zinc and phosphorous additives which necessitates certification to the older API SL standard. A good choice for owners of older Subarus, but could pose a threat to warranty coverage in newer cars which call for use of API SM or newer oil.

Motul 8100 Eco-Energy 5w30 – HT/HS 3.4
API SL, ACEA A5/B5
A high quality oil with high levels of zinc and phosphorous additives which necessitates certification to the older API SL standard. A good choice for owners of older naturally aspirated Subarus which call for 5w30, but could pose a threat to warranty coverage in newer cars which call for use of API SM or newer oil. Difficult to find and expensive, there is little reason to use 8100 Eco-Energy rather than functionally similar Mobil 1 High Mileage. Some Subaru dealers offer Eco-Energy as their premium fill.

Last edited by gpshumway; 07-05-2015 at 10:56 PM.
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Old 04-07-2015, 06:25 PM   #12
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10.5 Heavy Duty 30 grade Synthetic oils

Mobil 1 ESP Formula 5w30 – HT/HS 3.58
ACEA C2, ACEA C3, API SN (engine protection only), OEM approvals
A Low-SAPS oil designed for use in European passenger car diesel engines with particulate filters, but also for use in gasoline engines (VW 504). One of very few HD 30 grade oils which claim any conformance to API SN or SM standards. An excellent choice for owners of newer turbo Subarus who want to use an API SM or SN 5w30 for warranty reasons, but want the extra bearing protection afforded by a Heavy Duty oil. Builder specifications and ACEA C3 ensure good shear stability which has been confirmed through UOA. M1 ESP is not suitable for long drain intervals due to it's Low-SAPS, low TBN nature. Owners of direct injected European cars have noted that M1 ESP substantially reduces intake valve deposits compared to higher SAPS oils. Available at PepBoys and some auto parts stores catering to independent mechanics like CarQuest and NAPA. Generally quite expensive at around $10/qt.

Castrol Edge Professional European OE 5w30 – HT/HS 3.5?
API SM, ILSAC GF-4 (engine protection only), ACEA C3, OEM approvals
One of very few HD 30 grade oils which claim any conformance to API SN or SM standards. An excellent choice for owners of newer turbo Subarus who want to use an API SM or SN 5w30 for warranty reasons, but who want the extra bearing protection afforded by a Heavy Duty oil. Builder specifications and ACEA C3 ensure good shear stability which has been confirmed through UOA. Similar in many ways to M1 ESP 5w30, but capable of longer drain intervals due to being a High(er)-SAPS oil. Sold through European new car dealers (VW and BMW) and some specialty auto parts houses. Generally very expensive. Castrol doesn't publish an honest HT/HS for OE 5w30, only spec minimums.

Valvoline Synpower MST 5w30 – HT/HS 3.5?
API SN, ILSAC GF-5(emission system only), ACEA A3/B3/B4 & C3, OEM approvals
One of very few HD 30 grade oils which claim any conformance to API SN or SM standards. An excellent choice for owners of newer turbo Subarus who want to use an API SM or SN 5w30 for warranty reasons, but who want the extra bearing protection afforded by a Heavy Duty oil. Builder specifications and ACEA specs ensure good shear stability. Similar to M1 ESP 5w30. Difficult to find, but sold through some European new car dealers and some specialty auto parts houses. Generally very expensive. Valvoline doesn't publish HT/HS for MST 5w30, 3.5 is the spec minimum.

Motul 8100 X-Clean 5w30 – HT/HS 3.5
API SM, ACEA C3
A Low-SAPS oil designed for use in European passenger car diesel engines with particulate filters, but also for use in gasoline engines. One of very few HD 30 grade oils which claim any conformance to API SN or SM standards. An excellent choice for owners of newer turbo Subarus who want to use an API SM or SN 5w30 for warranty reasons, but want the extra bearing protection afforded by a Heavy Duty oil. Builder specifications and ACEA C3 ensure good shear stability. 8100 X-Clean is not suitable for long drain intervals due to it's Low-SAPS, low TBN nature. Some Subaru dealers offer X-Clean as their premium fill.

Castrol Edge 0w30 (a.k.a. German Castrol or GC) HT/HS – 3.5?
API SL, ACEA A3/B4.
The only reasonably available Heavy Duty 0w30 oil in the United States. GC is an excellent choice for heavy use in cold climates. High levels of zinc and phosphorous additives necessitate certification to the older API SL standard. Available at AutoZone stores. Castrol doesn't publish real HT/HS or many other specs like MRV and CCS for their products, only spec minimums, which makes detailed evaluation hard.

Red Line 5w30 – HT/HS 3.7
No formal certifications
A street/track oil composed of PAO and Ester base stocks and a very robust additive package high in zinc, phosphorous and especially moly. The moly acts as a friction modifier, giving this oil very low friction for its viscosity. The PAO/Ester base stocks combined with a lack of VII additives give this oil one of the best temporary shear ratios available. It is also extraordinarily shear stable, often showing no shear at all in UOA. These characteristics make it possibly the best oil available for heavy use in high temperatures, but performance improvements over 5w40 mixed fleet oils are dubious and the cost is double. Similar cold weather performance to 5w40 synthetics, not up to the best Light Duty synthetics. Despite a high initial TBN, rapid depletion means this oil is not suitable for extended drain intervals.

Motul 300V 5w30 – HT/HS 3.5
No formal certifications
Another street/track oil similar in purpose and composition to Red Line, but even more expensive. Given the greater availability and lower cost of Red Line, there's little reason to use 300V. Mentioned here only because it often comes up as the “ultimate” oil in forum discussions. Low TBN requires short change intervals.

10.6 Heavy Duty 40 Grade oils.

Shell Rotella T6 5w40 (RT6 for short) – HT/HS 3.8?
API SM, API CJ-4, ACEA E9
A long time forum favorite for turbocharged Subarus, which mostly means the EJ series. Marketed for HD diesel applications, but designed for use in gasoline engines too as evidenced by the API SM certification. Known as a “mixed fleet” oil because commercial vehicle operators with both light duty gasoline vehicles and heavy duty trucks can stock one oil for their entire fleet. Excellent shear stability ensured by ACEA E9. Robust enough for even highly modified engines in heavy use. If your engine “needs” a more robust oil than RT6, you should be looking for mechanical issues and/or installing an oil cooler. Cold weather performance is very good, but not quite as good as the best Light Duty 5w30 synthetics, adequate for the vast majority of users in the lower 48 states. RT6 is available at Walmart for about $5/qt, an excellent value. Shell does not publish HT/HS for RT6, but 3.8 is a reasonable minimum guess based on grade and specifications.

Mobil 1 Turbo Diesel Truck 5w40 (TDT for short) – HT/HS 3.8
API SM, API CJ-4, ACEA E7
Another mixed fleet oil marketed for diesel trucks but designed to work well in gasoline engines. All comments for Shell Rotella T6 apply to Mobil 1 TDT. Slightly more expensive than RT6, which accounts for its lower popularity.

Chevron Delo Synthetic 5w40 – HT/HS 3.8?
API SM, API CJ-4, ACEA E7
Another mixed fleet oil marketed for diesel trucks but designed to work well in gasoline engines. All comments for Shell Rotella T6 apply to Delo Synthetic 5w40. Slightly less available than RT6, but now in most Walmart stores. Chevron does not publish HT/HS for Delo 5w40, but 3.8 is a reasonable guess based on grade and specifications.

Mobil 1 0w40 – HT/HS 3.8
API SN, ACEA A3/B4, + OEM approvals
The most available 0w Heavy Duty oil in the United States. Carries many European OEM certifications. Suitable for year round heavy use in cold or warm climates. Good shear stability ensured by ACEA A3/B4, but not as good as ACEA E7 and E9 oils. Owners of direct injected European cars have noted higher levels of intake valve deposits with M1 0w40 than with Low-SAPS alternatives.

A note about 50 grade oils
Older Subaru owner's manuals mention 50 grade oil for heavy use. The benefits of using such oils over the available HD 5w40 synthetic options are dubious. The available oils all have substantial limitations, either low shear stability (Castrol 5w50, Eneos 0w50) or poor cold start performance (M1 15w50).

Acknowledgements:

I'd like to thank Ron (Unabomber) for his blessing to post this, and Dennis (bluesubie) for all his help editing.

Last edited by gpshumway; 04-08-2015 at 09:57 AM.
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Old 04-07-2015, 07:57 PM   #13
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Old 04-08-2015, 02:27 AM   #14
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BARV0.....

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Old 04-08-2015, 03:06 AM   #15
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Whoa that is a lot of information to process. Good job!! I will probably have to read this a few more times. Just curious, what oil do you run personally?
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Old 04-08-2015, 08:37 AM   #16
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You are crushed by gpshumway's Massive Wall of Text!
You take 246 damage.
You have died.

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Nice job buddy!
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Old 04-08-2015, 09:53 AM   #17
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Thanks for the encouragement, guys.

For the record, I currently use M1 ESP 5w30. I've used RT6, GC, and Red Line (both 5w30 and 0w30) in the past.
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Old 04-08-2015, 12:04 PM   #18
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Excellent! Well done. Only skimmed through it for now, but I look forward to reading it in detail later. It's nice to have all this information in the right place, and the Subaru-specific section will be really helpful. Thanks for your hard work on this, Ron and Dennis too.
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Old 04-08-2015, 12:18 PM   #19
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Nice job George P! I thought you used Alf oil??
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Old 04-08-2015, 03:13 PM   #20
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Quote:
Originally Posted by gpshumway View Post
Thanks for the encouragement, guys.

For the record, I currently use M1 ESP 5w30. I've used RT6, GC, and Red Line (both 5w30 and 0w30) in the past.
Thank you very much for taking the time to publish this on nasioc. I appreciate all of the information and will certainly be linking to this thread in the future

Also good to know Im on the right track, I am also using M1 ESP 5w30 in my '15wrx and RT6 in my 02 wrx.

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Old 04-08-2015, 04:32 PM   #21
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Quote:
Originally Posted by gpshumway View Post
Thanks for the encouragement, guys.

For the record, I currently use M1 ESP 5w30. I've used RT6, GC, and Red Line (both 5w30 and 0w30) in the past.
Really, good stuff. I learned. Also, M1 ESP 5w30 4eva!
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Old 04-09-2015, 09:34 AM   #22
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Will Castrol 5w30 OE from VW Dealerships work in the 2015 STI?
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Old 04-09-2015, 09:52 AM   #23
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Quote:
Originally Posted by gpshumway View Post
10.5 Heavy Duty 30 grade Synthetic oils

Mobil 1 ESP Formula 5w30 – HT/HS 3.58
ACEA C2, ACEA C3, API SN (engine protection only), OEM approvals
A Low-SAPS oil designed for use in European passenger car diesel engines with particulate filters, but also for use in gasoline engines (VW 504). One of very few HD 30 grade oils which claim any conformance to API SN or SM standards. An excellent choice for owners of newer turbo Subarus who want to use an API SM or SN 5w30 for warranty reasons, but want the extra bearing protection afforded by a Heavy Duty oil. Builder specifications and ACEA C3 ensure good shear stability which has been confirmed through UOA. M1 ESP is not suitable for long drain intervals due to it's Low-SAPS, low TBN nature. Owners of direct injected European cars have noted that M1 ESP substantially reduces intake valve deposits compared to higher SAPS oils. Available at PepBoys and some auto parts stores catering to independent mechanics like CarQuest and NAPA. Generally quite expensive at around $10/qt.

Castrol Edge Professional European OE 5w30 – HT/HS 3.5?
API SM, ILSAC GF-4 (engine protection only), ACEA C3, OEM approvals
One of very few HD 30 grade oils which claim any conformance to API SN or SM standards. An excellent choice for owners of newer turbo Subarus who want to use an API SM or SN 5w30 for warranty reasons, but who want the extra bearing protection afforded by a Heavy Duty oil. Builder specifications and ACEA C3 ensure good shear stability which has been confirmed through UOA. Similar in many ways to M1 ESP 5w30, but capable of longer drain intervals due to being a High(er)-SAPS oil. Sold through European new car dealers (VW and BMW) and some specialty auto parts houses. Generally very expensive. Castrol doesn't publish an honest HT/HS for OE 5w30, only spec minimums.

Valvoline Synpower MST 5w30 – HT/HS 3.5?
API SN, ILSAC GF-5(emission system only), ACEA A3/B3/B4 & C3, OEM approvals
One of very few HD 30 grade oils which claim any conformance to API SN or SM standards. An excellent choice for owners of newer turbo Subarus who want to use an API SM or SN 5w30 for warranty reasons, but who want the extra bearing protection afforded by a Heavy Duty oil. Builder specifications and ACEA specs ensure good shear stability. Similar to M1 ESP 5w30. Difficult to find, but sold through some European new car dealers and some specialty auto parts houses. Generally very expensive. Valvoline doesn't publish HT/HS for MST 5w30, 3.5 is the spec minimum.

Motul 8100 X-Clean 5w30 – HT/HS 3.5
API SM, ACEA C3
A Low-SAPS oil designed for use in European passenger car diesel engines with particulate filters, but also for use in gasoline engines. One of very few HD 30 grade oils which claim any conformance to API SN or SM standards. An excellent choice for owners of newer turbo Subarus who want to use an API SM or SN 5w30 for warranty reasons, but want the extra bearing protection afforded by a Heavy Duty oil. Builder specifications and ACEA C3 ensure good shear stability. 8100 X-Clean is not suitable for long drain intervals due to it's Low-SAPS, low TBN nature. Some Subaru dealers offer X-Clean as their premium fill.

Castrol Edge 0w30 (a.k.a. German Castrol or GC) HT/HS – 3.5?
API SL, ACEA A3/B4.
The only reasonably available Heavy Duty 0w30 oil in the United States. GC is an excellent choice for heavy use in cold climates. High levels of zinc and phosphorous additives necessitate certification to the older API SL standard. Available at AutoZone stores. Castrol doesn't publish real HT/HS or many other specs like MRV and CCS for their products, only spec minimums, which makes detailed evaluation hard.

Red Line 5w30 – HT/HS 3.7
No formal certifications
A street/track oil composed of PAO and Ester base stocks and a very robust additive package high in zinc, phosphorous and especially moly. The moly acts as a friction modifier, giving this oil very low friction for its viscosity. The PAO/Ester base stocks combined with a lack of VII additives give this oil one of the best temporary shear ratios available. It is also extraordinarily shear stable, often showing no shear at all in UOA. These characteristics make it possibly the best oil available for heavy use in high temperatures, but performance improvements over 5w40 mixed fleet oils are dubious and the cost is double. Similar cold weather performance to 5w40 synthetics, not up to the best Light Duty synthetics. Despite a high initial TBN, rapid depletion means this oil is not suitable for extended drain intervals.

Motul 300V 5w30 – HT/HS 3.5
No formal certifications
Another street/track oil similar in purpose and composition to Red Line, but even more expensive. Given the greater availability and lower cost of Red Line, there's little reason to use 300V. Mentioned here only because it often comes up as the “ultimate” oil in forum discussions. Low TBN requires short change intervals.

10.6 Heavy Duty 40 Grade oils.

Shell Rotella T6 5w40 (RT6 for short) – HT/HS 3.8?
API SM, API CJ-4, ACEA E9
A long time forum favorite for turbocharged Subarus, which mostly means the EJ series. Marketed for HD diesel applications, but designed for use in gasoline engines too as evidenced by the API SM certification. Known as a “mixed fleet” oil because commercial vehicle operators with both light duty gasoline vehicles and heavy duty trucks can stock one oil for their entire fleet. Excellent shear stability ensured by ACEA E9. Robust enough for even highly modified engines in heavy use. If your engine “needs” a more robust oil than RT6, you should be looking for mechanical issues and/or installing an oil cooler. Cold weather performance is very good, but not quite as good as the best Light Duty 5w30 synthetics, adequate for the vast majority of users in the lower 48 states. RT6 is available at Walmart for about $5/qt, an excellent value. Shell does not publish HT/HS for RT6, but 3.8 is a reasonable minimum guess based on grade and specifications.

Mobil 1 Turbo Diesel Truck 5w40 (TDT for short) – HT/HS 3.8
API SM, API CJ-4, ACEA E7
Another mixed fleet oil marketed for diesel trucks but designed to work well in gasoline engines. All comments for Shell Rotella T6 apply to Mobil 1 TDT. Slightly more expensive than RT6, which accounts for its lower popularity.

Chevron Delo Synthetic 5w40 – HT/HS 3.8?
API SM, API CJ-4, ACEA E7
Another mixed fleet oil marketed for diesel trucks but designed to work well in gasoline engines. All comments for Shell Rotella T6 apply to Delo Synthetic 5w40. Slightly less available than RT6, but now in most Walmart stores. Chevron does not publish HT/HS for Delo 5w40, but 3.8 is a reasonable guess based on grade and specifications.

Mobil 1 0w40 – HT/HS 3.8
API SN, ACEA A3/B4, + OEM approvals
The most available 0w Heavy Duty oil in the United States. Carries many European OEM certifications. Suitable for year round heavy use in cold or warm climates. Good shear stability ensured by ACEA A3/B4, but not as good as ACEA E7 and E9 oils. Owners of direct injected European cars have noted higher levels of intake valve deposits with M1 0w40 than with Low-SAPS alternatives.

A note about 50 grade oils
Older Subaru owner's manuals mention 50 grade oil for heavy use. The benefits of using such oils over the available HD 5w40 synthetic options are dubious. The available oils all have substantial limitations, either low shear stability (Castrol 5w50, Eneos 0w50) or poor cold start performance (M1 15w50).

Acknowledgements:

I'd like to thank Ron (Unabomber) for his blessing to post this, and Dennis (bluesubie) for all his help editing.
Quote:
Originally Posted by fenderpicks View Post
Will Castrol 5w30 OE from VW Dealerships work in the 2015 STI?
it took me about 3 seconds to figure this out
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Old 04-09-2015, 10:09 AM   #24
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great stuff. i'd love to see you go into more depth about 50 & 60 weight oils and their racing application
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Old 04-09-2015, 11:33 AM   #25
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Quote:
Originally Posted by vicious_fishes View Post
great stuff. i'd love to see you go into more depth about 50 & 60 weight oils and their racing application
Band aid, nothing more.

"Racing" applications tend to be adapted street cars, and often don't have the highest analytical standard in their design, lots of wives-tale engineering. The other thing that gets confused is that light street oils also have lower levels of traditional anti-wear additives, so "race" engines derived from old pushrod designs with stiff valve springs and flat tappet cams use 50 grade oils like M1 15w50 simply for the additive package. They need the additives, not the viscosity (generally speaking), but in street oils they come as a package deal. In pure race oils you get those sky-high additive levels in any grade you want down to 0w10.

Real race cars simply size the oil cooler to run thin oil. Joe Gibbs Racing uses pushrod engines to insane RPM and doesn't use anything thicker than 20 grade for races (at least according to their oil site), and they use straight 0w for qualifying! Remember, thick oil costs horsepower! In a street car it's not enough power to worry about, but in a race car where you're trying to shave tenths of a second per lap, it matters.

http://www.drivenracingoil.com/dro/c.../synthetichtml

The next time some BMW owner who proves the porcupine joke talks about how good 10w60 is, just smile knowing it's a band-aid BMW had to use to prevent their precious M engine from eating it's own bearings.
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