Jason Teller

I could be crazy but it seems like my car just runs better with 94 octane as opposed to 92 or 91. Here in Ontario it is more difficult to find 94 -- they definitely don't have it everywhere. My last tank made my car idle a little rough I think. But I filled up with 94 today and it's better already...<p>Jason

GeorgeC

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donp

I notice a difference between *brands* of fuel which are supposed to be the same octane. My car runs best on Shell 93 and absolutely sucks on Chevron 93. Go figure.

Albert

Just had ARCO come into my school, and I just spoke with the chairwoman, who confirmed what I already knew, everybody uses the same gas; they buy gas from the distributor and so all your gas is the same. Brands don't matter, it's the octane rating, which determines your knock index. Higher octane will give you smoother ride, quieter idol, less knocking, and probably better gas mileage.<p>Albert

pjay

What does the manual suggest? Is your car chipped that requires the higher octane gas?

Gary B

Janson<p>Most modern cars will advance or retard their timing based on the grade of fuel used. This allows the peak performance from every tankful of gas rather than in the old days with the static timing and set advance. This is why the Audi can run on 87 octance fuel although it's recommended you use 91.<p>Gary B<br>1.8tqms

eliot

all the v6 engines including the 12V have ignition advance that can take<br>advantage of 94 octane gas. therefore you will not be getting full power<br>with 92 octane, let alone 89 or 87.<p>it is a lie that all gasoline brands are the same. gas contains several hundred<br>ingredients. the cheap crap like arco has a lot of alcohol in it. alcohol has<br>a poor sensitivity rating. i.e. its unloaded octane rating (RON) is high, but its<br>loaded (MON) rating is low, thus your effective octane rating is lower than<br>the R+M/2 rating, since you need octane when your engine is loaded.<p>the good gas are the ones with a high aromatic content. aromatics have a<br>very high MON rating, thus they are ideal for high strung, high pressure turbos.<br> i have been enhancing the aromatic content in the gas myself. the results are terrific. my 1.8T with stock boost doesn't seem to care, but my other cars<br>showed major improvements.. (v8q, 993) my friend's corrado vr6 also went<br>nuts with the stuff. <p>the aromatic content in US gas is very low compared to europe and asia.<br>this is due to corn farmers' lobbying and (IMO) misguided well meaning<br>environmentalists. consequently the gas sold here is of an inferior quality<br>to high performance engines compared to equally rated octane gas sold in other<br>countries.<br>.<br>when they finish installing the 1 bar wett chip on my 1.8t you can be sure <br>that i will be running a lot of rocket fuel in it. drop me some email if<br>you want to hear more.<p>eliot<br>

Tomasz

That is interesting. I found my Neuspeed chipped car to emit more smelly emissions (under full throttle) when running on Chevron 93. I will try Shell at my next fill up.

RobP

But not all additives are the same--> brand does matter

roger

Yes, most gas stations get their gas from their local fuel depot. In fact, fuel is a traded commodity. So just because you buy gas from Chevron, doesn't mean they didn't get some of the gas from Shell. Anyway, like I was saying, what differentiates the gas at the pump is that Chevron truck guy, after filling up his tanker with gas, adds chevron specific additives, and the Arco guy does the same thing. So the gas isn't exactly the same. <p>-Roger