I love to research car stuff, and since I was due for an oil change, I have been researching oil lately. Here is what I have, I figured I would share it with everyone.

Motor Oil Specs

Viscosity at XXX C - Self explanatory, the viscosity of the oil at said temp. A lower value at low temp is better as it means the oil will flow easier during start-up. A higher value at high temp is better as it means the oil is maintaining its protection abilities (a thin oil will not protect well at all under stress).

Viscosity Index - Rates oils ability to maintain a viscosity over a wide range of temperatures. A higher value is better, and should not be below 130.

Flash Point - Temp at which the oil vaporizes sufficiently for it to ignite. Obviously, a higher flash point is better, and it should not fall below 400 F.

CCS - Cold Crank simulator. This tests an oils ability to start well at cold temps. This is basically a viscosity rating. A lower value is better, but take into account that testing is done at different temps, so it is difficult to compare.

HTHS - High Temp High Sheer. A highly useful test that simulates oil sheer and stress under running-engine conditions at 150 C. A higher value is better, as it shows that anoil will keep a consistent viscosity even under increased temp and stress.

NOAK - A test where the oil is monitored for one hour in a 250 C environment. The rating is the percentage of the oil that evaporates in this time. Lower is better, as it shows that the oil will not vaporize and degrade under extreme temp situations. For the numbers of this taken from the Oil Bible Document, there were way too many 13% values for it to be accurate. I think that the info. Was unavailable and this is a safe assumption, but it most likely is not the actual value.

Oil Bible Rating - The author of the oil bible document (link found in the Oil FAQ) rates oils by plugging the different test values into a formula that produces a number that shows the overall quality of the oil. Higher is better, as it represents a solid performance over the range of tests. In all truth, I am not sure how it works or how accurate it is, but the guy who does it knows his stuff, and I though I would include it anyway.

Redline Synthetic 5w30
Viscosity @ 100 C - 10.6
Viscosity @ 40 C - 62
Viscosity Index – 162
Flash Point – 486 F, 252 C
CCS – 6000 @ -30 C
HTHS @ 150 C – 3.8
NOAK – 6%
Oil Bible Rating – 707
High quality oil, posts some good numbers and is highly recommended by many on various sites. This is one of the two oils I am considering for my car.

Redline Synthetic 10w30
Viscosity @ 100 C – 10.7
Viscosity @ 40 C – 70
Viscosity Index – 142
Flash Point – 480 F, 250 C
CCS – 6500 @ -25 C
HTHS @ 150 C – 3.8
NOAK – 6%
Oil Bible Rating – 710
I had originally planned on using this in my car, but after comparing, the 5w30 seems like a better oil overall. I found this odd. However, this is still a very nice oil.

Amsoil ASL 5w30
Viscosity @ 100 C – 10.6
Viscosity @ 40 C – 57.3
Viscosity Index – 178
Flash Point – 442 F, 228 C
CCS – 5254 @ -30 C
HTHS – 3.2
NOAK – 6.6%
Oil Bible Rating – 759
Both Amsoils impressed me with their numbers. These are as good, and probably better than Redline oils in my opinion. The problem with them is that they have to be ordered.

Amsoil ATM 10w30
Viscosity @ 100 C – 10.7
Viscosity @ 40 C – 59.8
Viscosity Index – 171
Flash Point – 442 F, 228 C
CCS – 4020 @ -25 C
HTHS – 3.2
NOAK – 5.4 %
Oil Bible Rating – 742
Very nice oil. Unlike Redline, the 10w30 seems to be just as good as the 5w30, but the minimal extra high temp protection is still odd.

Castrol Synthetic 0w30 (German Castrol)
Viscosity @ 100 C – 12.1 (Oil Bible)
Viscosity @ 40 C – ?
Viscosity Index – 175 (Oil Bible)
Flash Point – 437 F (Oil Bible)
CCS – 6200 @ -35 C
HTHS – 2.95 (Oil Bible)
NOAK – 13% (Oil Bible)
Oil Bible Rating – 686
This oil is considered a Magical Elixir by many on BITOG. Looks like very nice stuff, gets good reviews and UOAs, but Castrol’s uninformative spec sheets have me wondering a little bit. Only available at Autozone. This is what I ended up putting in my car.

Mobil 1 Turbo Diesel Truck 5w40 (Delvac)
Viscosity @ 100 C – 14.8
Viscosity @ 40 C – 102
Viscosity Index – 151
Flash Point – 226 C
CCS – 6600 @ -30 C (Oil Bible)
HTHS – 2.90 (Oil Bible)
NOAK – 13% (Oil Bible)
Oil Bible Rating – 682
Used by Truckers on long hauls, this is a good oil but is hard to find. I’d heard about it and decided to look it up, and I may try it in the future.

Mobil 1 synthetic 5w30
Viscosity @ 100 C – 11.3
Viscosity @ 40 C – 64.8
Viscosity Index – 169
Flash Point – 230 C
CCS – 6600 @ -30 C (Oil Bible)
HTHS – 3.09
NOAK – 13% (Oil Bible)
Oil Bible Rating – 684
Very popular oil that is widely used, and apparently for good reason. Good scores and universally available. I used this in my first oil change, and it did very well, but I did notice a about ¾ quart consumption over ~8500 miles.

Royal Purple synthetic 5w30
Viscosity @ 100 C – 11.0
Viscosity @ 40 C – 65.3
Viscosity Index – 161
Flash Point – 455 F
CCS – 6600 @ -30 C
HTHS – 2.9 (Oil Bible)
NOAK – 13% (Oil Bible)
Oil Bible Rating – 645
I have this in my engine right now. I’ve been running it for 6,000 miles. I’ve noticed a little more consumption than I would have expected (around ¾ quart), and mileage seems to have dropped a tiny bit. A good oil, but I think there is better for the money.

My Observations: It is hard to tell which is the best oil out of these, even with the specs to compare against each other. Some oils outperform the others in one area, only to perform worse than the others in another area. One trend I did notice is that the 5w30 oils seem to perform better than the 10w30 oils in most areas. I found this very surprising, as I thought 10w30 had no additives and was as stable as you could get.
On the whole though, it seems that if you buy a quality synthetic oil in the correct weight for your application, you probably won’t be able to tell a difference. Which is what everyone has known from the beginning. Hmm…. Almost makes this seem like a waste of time.

PLEASE NOTE: The above values came from two sources: the spec. sheets available on the respective manufacturer’s website, and the Oil Bible Document, which has a table that lists the specs of almost every oil ever made. The specs listed are those from the manufacturers except the ones that say Oil Bible next to them. This means the company did not provide that spec on the oil’s sheet. This should be taken into account, as there is usually a reason a company does not release a certain test result.

I love to research car stuff, and since I was due for an oil change, I have been researching oil lately. Here is what I have, I figured I would share it with everyone.

Thanks, good stuff! I was thinking about going to synthetic with extended drain intervals, and I've been looking into it too. Searching various places including here & bobistheoilguy.com (www.bobistheoilguy.com).

In the end I decided on Redline synthetics gear oils, but chose a good inexpensive "dino" oil off the shelf for my upcoming motor oil change (Formula Shell 5-30 API SM/ILSAC). Might go to synthetic motor oils & extended drain intervals next oil change. I think they buy you less in the engine than in the MT. I'll look for one with low viscosity loss over time. Speaking of which, are you going to do an oil analysis on your used Royal Purple? It didn't make the cut of oils I was looking at, but it might be great stuff--I didn't look that closely.

Castrol Synthetic 0w30 (German Castrol)
Viscosity @ 100 C – 12.1 (Oil Bible)
Viscosity @ 40 C – ?
Viscosity Index – 175 (Oil Bible)
Flash Point – 437 F (Oil Bible)
CCS – 6200 @ -35 C
HTHS – 2.95 (Oil Bible)
NOAK – 13% (Oil Bible)
Oil Bible Rating – 686
This oil is considered a Magical Elixir by many on BITOG. Looks like very nice stuff, gets good reviews and UOAs, but Castrol’s uninformative spec sheets have me wondering a little bit. Only available at Autozone. This is what I ended up putting in my car.
SO it's OK to put 0w30 in our Subarus? It looked cool to me, but since they're speced for 5w30, 10w30, etc, but not that one I didn't know if it was OK.

Castrol Synthetic 0w30 (German Castrol)
HTHS – 2.95 (Oil Bible)

I believe GC has a minimum HTHS of 3.5 or 3.6 because it meets A3 ratings. Just spouting stuff I read on BITOG a while back.

And nice summary on the oils :cool:

Davidji-
For the most part, you can run almost any oil in your car that you want to, depending on your driving conditions. I've read about people running 10w40 for track days, and some people run even heavier. 5w30 is what SOA reccomends for the everyday driver who only presses the car so far. For aggressive street driving, 10w30 is probably as heavy as you should go.
As for the 0w30, its fine to run. In my opinion, its better than the 5w30 because its thinner at startup, which reduces wear and warm-up time. Its not very commonly run because not many oil companies make a 0w30 oil. The German Castrol stuff has been really nice in my car so far: engine runs a tad smoother and it warms up in about 2/3 the time it used to. Plus, GC is pretty thick at high temp for a 30 weight oil, so it fits my "spirited" driving style well :banana:

0w30 is also thinner at temp then 5w30 unfortunately. o

0w30 is also thinner at temp then 5w30 unfortunately. o
Nope, that's old school thinking. :) It all depends on the oil.

I had to switch to something thinner for winter because Castrol Syntec 0W30 (GC) is too thick for my application (five mile trips each way) and my fuel dilution was too high last winter. GC is 12.1 Cst's at 100C.

-Dennis

^^^^^ What he said. GC has a 100 C viscosity of 12.1. 5w30 and 10w30 oils from Amsoil and Redline are 10.6 and 10.7. A higher number means a thicker oil.