With gas prices going up, I was wondering if gas is gas? I almost always go to Chevron for gas, not 100% sure why, maybe it's the commercials with the cars or what. Is 92 at one gas station the same as another?

I'm no professional gas guy, and I don't know the difference between octanes. But I did talk a little about this with a friend who used to work the night shift at a local station... If someone disputes what I say, take their word for it.

My oppinion is that a certain octane will not be the same between two different stations. Not that it's going to be drasticaly different, but it will not be the same. I'd say that within the same station it will be different from week to week even...

-Silas

ONLY Chevron Premium for my car.

As with everything there are tolerances that need to be adhered to, to say a gas is x octane (ie 92 octane can range from 91.2 to 93 and still be considered 92)... the difference lies in the other stuff in gasoline. The purity and additives are really what seperate gasoline. That's one of the reasons that name brand gas costs more. In most cases it has more detergents and is a more pure form of petroleum. This results in less deposits and reduced engine wear. Of course the effects are somewhat minor short term and can even remain that way in the long term. But some people who need the best for their vehicles will not settle for impurities of any form ..

Brad

As Brad mentioned, it is the fuel additives that mainly differentiate gasoline brands. Some common additives:

* Ethyl Alcohol (reduces emissions)
* MTBE or methyl tertiary butyl ether (increases octane and also reduces emissions)
* detergents (help keep your engine clean)
* anti-oxidants (prevent deposits)

There are others, but those are the most popular in the US.

Jordan

I don't know much about gas but a lot of people on this club say "just use regular, that's what the car was made for" and "anything higher is a waste of money." Well race cars use 100+ octane, so I'm sure it has to do something.

MagicMT-
Yes, it does do something, but that doesn't mean that it will be something good for your particualr car. A gasoline's octane rating measures its resistance to pre-ignition. As the fuel-air mixture in the cyllinder is compressed by the piston, the temperature and pressure increases (per Universal Gas Law), and it can reach a point where the mixture will burn before the spark plug ignites it. That is pre-ignition, and it causes a shockwave to hit the piston head as it is still moving up, which makes the "knock" sound you may be familliar with. This reduces engine efficiency, and in extreme cases can damage the engine. Engines with a higher compression ratio create a larger change in temperature and pressure inside the cyllinder, and therefore have a higher risk of pre-ignition. The presence of iso-octane in gasoline increases the threshold for pre-ignition, and higher octane ratings can withstand higher compression ratios.

So, the bottom line is, if your engine manufacturer recommends a certain octane rating for your engine, then you have no reason to use a higher octane rating. There will be no increase in performance unless you somehow modify the internal workings of your engine. Adding a turbo or changing the compression ratio are good examples of mods that may require an increase in fuel octane.

Here's a link to a more complete explanation: http://www.pcf.ab.ca/quick_answers/gasoline_general/octane_rating.asp

Hope this helps
Jordan

[This message has been edited by Poseidon (edited April 24, 2001).]

en3d - The answer is no. Not only is the gasoline formulation different between brands, but a brand (such as Chevron for instance) may change their formulation from season to season, and the formulation is likely to evolve over the years.

This means that sometimes, when you notice problems with the way your car is running, it may be worthwhile to run a couple of tanks of a different or better brand of gasoline. If you have a good mechanic, or knowledgeable friend who tunes high performance engines, they may recomend brands. My mechanic asked me to stop using ARCO gasoline for a problem I was having with a Nissan 280ZX. I switched to Shell, and it did help to reduce the problem.

BTW, I was reading an article in the Los Angeles Times this morning that indicated that here in Califonia, the major urban areas have special summer gasoline formulas to help reduce the polution. This formulation is more expensive, because it uses MTBE, and this chemical is obtained from natural gas, not petroleum. Natural gas is priced high now, consequently our summer gasoline formula will be even more expensive than usual. yippee!

There's more than you probably wanted to know...

this is what i'd do. from my experiances.

i have a harley, 89 5.0 mustang and MY00 RS impreza. used to have a 92 FZR 600 also.

my mustang runs the best on regular 76 the fule of NASCAR

my harley i still havn't found out but i know it sounds great with cheap as$ gas

my impreza loves Chevron mix regular and plus. and i run half tank for weight. never know when ur goin to get that nice late night race!

my yamaha FZR ran the best on chevron primium. wich also gave it the best performance and sound. (nice hummmm)

i don't know if it makes a differance but go try different brands. maybe even a mix. and there is no point in running a fule additive when u run premium gas.


just my .02

dean

actually mtbe was thought to be better for the gasoline and better for emissions but recently scientists have found that mtbe is actually making emissions worse hurting the enviroment more too. thats why california outlawed the use of mtbe in all gasoline. if you go to chevron you will see a sticker on the gas pump talking about it. also to add about different octanes the person above said it perfectly and would just like to add that the higher the octane the slower the fuel mixture burns which makes higher octane gas less prone to premature detonation.
peace

So octane boosters don't do crap? They claim it adds HP...

Higher octane does not add horsepower on its own. Higher octane allows the car to run higher compression (or higher boost).

Higher compression/Boost = More air.
More air = More HP.

Internal combustion 101. Got it?
www.howstuffworks.com (http://www.howstuffworks.com) is a good place to go to learn the basics of how this stuff, well, works. =)

I have talked to several people I know in the automotive field and one is a fuel distributor and he has told me that for the average engine there is no difference in gas from one station to the next. And he sells Texaco and Shell and deals with the Chevron guys sometimes.

Just relaying what I've been told

MTBE is made from Natural Gas AND petroleum. It is a reaction of Methanol (usually made from nat. gas) and butylene (which comes from oil, mostly created in the fluidized catalytic cracking unit). The only noticable difference in gasoline from one station to another is the additives. If you live in a town where there is a refinery, practically EVERY station in that town uses the gasoline from THAT refinery. For example, if you live in Lake Charles, LA, and there are a conoco and a citgo refinery in that town, every chevron, every exxon, every shell, every mobile, every diamond shamrock is getting its gas from on of the two refineries. The additives (techron, etc) are added as the gasoline is loaded into tanker trucks.

I had a couple of previous cars that were very finicky for octane (XR4Ti, Saab 900T) and I found that Shell, BP (before they became part of 76), and Sunoco (on the right coast..mmmm 94) were consistently ok.

I had terrible problems with Chevron premium and it is one that I still avoid to this day.

Texaco is so-so.

I'm back again to the stage where I have three cars that require premium!

Glenn

Concerning MTBE: It is no longer being used in California due to concerns over water supply contamination, not because it increases emissions (which it does not).

Jordan

Poseidon

3 days ago at the pump it said this gas has MTBE in it.

Glenn

never knew my company had been aquired by the owners of 76 stations ??? When did this happen ?

Brad a bp employee

MagicMT: I think you're missing the point- higher octane can give you an increase in power- but at some point, every engine reaches its maximum potential for making power- the 2.5RS engine was designed for regular pump gas. Period. A race car sucks in much more air, and gas, and runs at combusts at higher temperatures, so it can benefit from higher octane gas. Read the posted link.

So...

If you have a car, in stock form, that requires 87 octane gas.... then it will run best with 87 octane gas (duh).

If you have the same car, with a modified air intake and exhaust, would putting in 89 or Premium gas give slightly better performance?

Running higher octane will NEVER give you more HP.

If you your engine is pinging, the ECU will change the timing to avoid detonation. If you start using a higher octane fuel, then your ECU doesn't have to do that and will adjust the timing back to normal parameters, and your engine will run more efficiently.


As for your question, Remarcable. When you add more air/fuel volume to the cylinder per stroke, you are increasing the compression, and increasing the chances of detonation, which is why turbo setups have to run higher octane.

It seems unlikely that an intake alone would increase the volume enough to require a higher octane, but you never know. You could try stepping up to 89, and see what happens, but I don't think you need to.

Yes, they found high levels of MTBE in ground water from all the gas spilled on the ground at stations, and it's a known carcinogen.

They'll probably just switch over to Ethanol, which is what they run here, from October to May. The oxygenated fuel really takes a chunk out of your mileage.

Additives (in California): MTBE is still used at most stations in the Bay Area, at this time. Some 76 stations are switching to Ethanol, but the majority are still MTBE. (Local car geeks are actually recommending avoiding the Ethanol stations, for now - MTBE being appearantly slightly better for the engine? May just be preference)

Off Brands: Just because you're buying your gas from some independent station, doesn't mean your gas is any different then the stuff you buy at Shell/Chevron/etc... Independents buy gas from whomever sells it to them at a price they'll pay - they could be Chevron one week, and Shell the next (potentially) The octane rating should be as advertised, but the source of the gas may vary. Picky? Buy from a chain. Personally, I buy from an independent most of the time, but will stop at a chain if it's convienent - saving 10c/gallon isn't worth driving out of my way.

Octane: Higher octane gas is less likely to detonate early when compressed. If your engine is stock, use what it's rated for - UNLESS you get knocking, then go up a grade. If your engine is rated for 86 octane, it's designed to not pre-det with 86 octane. 92 means it's less likely to pre-det, but unless you've changed the compression, you shouldn't need it. Turbo and supercharged engines, due to running at higher compression, need higher octane generally - thus, the WRX needs 91 octane, but the 2.5RS can get by on 87 (I think?)

Anyways, no, I'm not really a car geek, but this is what I've picked up from talking to them, so I may have made a mistake here, but I think this pretty much sums it up.

Bottom line: Gas is gas, mostly... For your average person, the variances won't matter. Use the suggested octane, and only increase if it pings. Avoid Arco. (Actually, that's just my opinion, since I don't like them charging to use plastic ;-)

I don't know about my subaru's ecu, but my ford f150's ecu will adapt (over a period of time)to higher octane by advancing the timing to give a little extra power. I would think most modern autos can adapt to higher octanes by adjusting the timing on their own. I now run a superchip in my truck which requires 92 octane and runs a program that gives me 25 extra hp. I wish they made one for my sube!


Doug

I don't care what you guys say... My car runs better on Premium. Period. I drive my car everyday, and I can tell a difference. If you wanna use regular, have at it. If someone wants to use premium cause it makes their car run better, then great.

-Bill

Zahnster-

Pardon my jumping the gun:


On March 25,1999 California Governor Gray Davis issued an Executive Order "...for the removal of MTBE from gasoline at the earliest possible date, but not later than December 31, 2002."


It is being phased out, but may still be in use in some places in CA.

Jordan