The fact is, ANY octane higher than that which is necessary to prevent the engine from knocking does nothing to improve performance. Octane's only purpose is to increase the pressure level at which point the fuel will combust. It has absolutely NO benefit to performance. If your car does not have pre-ignition using 91 octane fuel, using a fuel of a higher octane will be of no benefit. In the USA, the EPA dictates that ALL fuels have the same level of detergents, so claims that running a higher octane fuel will keep your engine cleaner is also a myth.

 

So are you saying that advancing the timing does not create ANY added power ?

 

No. I ment exactly what I said. If you modify your timing to be more advanced than stock, then assuming everything remains constant, you might need a higher octane fuel if knock is present. However, the increase in octane does not improve performance...advancing the timing (within limits) might.

 

I often mix 1/4 100 and 3/4 91 to produce 93. I notice a difference. The engine does not have the same initial hesitation as with 91 (very small difference). I think it is more important to buy "top tier" gas than 93 vs 91. Shell and Chevron are top tier fuels.

 

I noticed someone said something about octane booster. does that stuff actually work?

 

I don't know, but I don't think I would use a product like that. I don't think the products say what the octane boost is after adding it, so what are you actually getting?

 

Usually advancing the timing does not improve much. In some engines it does in other it does not. If it does anything it only helps on accelleration.

 

Porsche recommends 93 for my GT3. At the track I mix 91 & 100 50/50 to get roughly 96 octane. There's a noticeable difference between that and plain 91. I've also run straight 100 and it's no better than my 96 blend, hence it's just pissing money away. So, the sweet spot for my car is somewhere between the 93 that the factory suggests and my 96 mix.

 

The manual says the car will know when less than 93 octane fuel is used and engine adjustments occur automatically. Do you have to make any engine adjustments to take advantage of fuel with an octane rating over 93? I also notice a difference when I mix 100/91, but I have never attempted to validate this with actual testing. Have you?

 

I don't know if there's any advantage to using >93 with the stock set up. I'm sure there are tuners that sell programs to take advantage of higher octane, but I wouldn't go there since I like my warranty, trust Porsche's engineering, etc.

The only testing I've done is with my butt at the track. It's clear that the car pulls stronger with the higher octane. How much I have no idea, but it's real & noticeable. There's no difference that I can tell between 91/100 and straight 100, so >91/100 is wasting money IMO.

 

Best link I've seen with references:

http://theserviceadvisor.com/octane.htm#1

 

Thanks for sharing - according to that site the 100 octane at my local station is pointless and "I would be giving money to the gas company and gain no benefit." Looks like the lines of M3's who use this 100 are also wasting their money....

I guess I will pass on this....

 

A pretty wise old guy once told me that using gasoline with higher octane than is recommended for your car is like wearing shoes that are a size too big. They don't make you any faster.

 

the old man is flawed. bigger shoes would make you slower...

 

I wise old man once told me "Replying to threads that are 3.5 years old is a waste of your time and the others who read them thinking it's a new thread."