CALSE

Does anyone know what the highest octane fuel mixture the stock tune will efficiently accommodate?

LexVan

2 summers ago, I played around and used a ton of 98 octane unleaded. No track duty. The only difference I felt was in my wallet ($8.00/gallon....IIRC). My right foot was telling my left brain the cars felt faster, but someone was BS the other. I think a stock tune maxes out at just over 93 octane.

Nick Yoskin

oxygenated fuel is what you need. That will make more power.

LexVan

I think you mean unoxygenated...... meaning without any ethanol. Pretty hards to find in 93 octane. Yes for 91. Some tracks have no ethanol 93 or 98. North of $6/gallon.

Haku

No ethanol 93 is def the way to go. Much better in every way.
Hopefully it's available in your state.
http://pure-gas.org

Mike in CA

There's no point in using fuel with higher than 93 octane as Porsche states max performance is achievable with 93. For the street the 91 that is readily available is adequate. For timed events, I buy some expensive 100 octane unleaded and blend a few gallons with my the 91 in the tank to bring the average up to 93+. I don't know how much difference it makes, but I feel better about it.

Drifting

Is a California thing that you guys don't have 93 octane available anywhere in the state? 93 octane is available in most states on the East Coast.

Also I agree with both you and Haku. With you that buying more than 93 octane doesn't accomplish anything. I agree with Haku that the ideal gasoline for our GT3s would be 93 octane without ethanol

sk0t

My dealer in Adelaide also recommended against ethanol-blended fuels. I plan to run the same Mobil 98 RON fuel (US 93-94) that I've used almost exclusively in my STi and RS4.

Mike in CA

You East Coast guys are lucky with regard to the 93 octane. California is generally only 91 octane. Nevada and Arizona and the Rocky Mountain States too, I think but maybe RL'ers from those areas can confirm.

hzoenvy33

I always wondered how the GT3 engine is able to make 475hp in the US with 93 octane and in Europe you have to put in 98 octane to get 475hp while 95 octane means "reducing" peak power....

sk0t

Because the US octane numbers are the average of RON and MON, which is also known as the AKI (Anti-Knock Index); see http://en.wikipedia.org/wiki/Octane_rating for more details.

Bacura

Which is better. 91 with no ethanol or 93 with ethanol? Those are my 2 choices. Shell is the 91 no ethanol and is nitrogen enriched whatever that means.

Haku

I would go with 91 No Ethanol. I have no scientific knowledge to base my preference on, I just don't like ethanol and the damage it does to hoses and engines.

LexVan

I always say octane rules. So. I'd take the 93 with ethanol. Most fuels I've tested with my ethanol testing kit shows ethanol levels right around 5%. Max I've seen was 9%. I think they do this to be within a safe range for the legal claims at the pump, "less than 10% ethanol".

A modern Porsche is built for these 10% ethanol levels.

When storing your car for a few months, make sure the tank is very-very full, and stabilize the fuel with a product like Sta-Bil at a minimum of 1 ounce per 2.5 gallons fuel. Double dose for storage exceeding 6 months.

Nick Yoskin

Nope....e15 and oxyoganted fuels are two completely different things. Google it.