IDGTCS

My 2007 GT is stock except for a K&N CAI. In my region of Idaho virtually all of the gas stations blend in 10% ethanol with their gas. Given that, is there any benefit to running 89 or 91 octane with a factory tune? With non-ethanol gas is the answer the same? I understand that ethanol has less energy per gallon than gasoline.

I have been running 89 octane, but have not really put many miles on the car since I bought it 3 months ago. I have not run it under high load or high temperature conditions so I don't have personal experiece to go on.

BruceH

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157dB

No gains without the tune.
The C&N dont require a tune so a tune wont help there either.
Higher octains for the set OEM timing tables is a waste of $$.
The ethanol is not going to be nice io your fuel system thats not designed for it.
If it says 89 Octiae and is an Ethanol blend, you can bet it is 89 Octane.
They compensate for the less BTUs available from the 10% Ethanol.

IDGTCS

Thanks for the information. This will save me some money.

It is worth avoiding ethanol blended gas in my car? I can get straight gas near Boise but have to drive a little further.

Nuke

If you can get gas w/o the ethanol than go for it. But I wouldn't go TOO much out of my way. Every once in awhile I get a tank of gas that I suspect has more than the labeled 10% and the car runs pretty bad and the mileage sucks. And as stated, you won't gain anything going to a higher octane on the stock tune. But if you want performance and still want to use 87 octane, get a custom tune. Even the 87 custom tune puts the stock 87 tune to shame.

BruceH

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IDGTCS

Thanks for all of the feedback. I would avoid ethanol if it was around the corner but it requires a drive that negates the added mpg.

I will stick with 87 octane though.

alkemist

+100

My 87 custom tune kicks azz. I'm afraid to see what the 91 does lol.

Well, when the mod bug bites you and you're ready to step it up, I would recommend getting a custom tune

RainsFather

one thing you should be careful about running e10, if you do get a tuner and get an email tune from somebody make sure that they know that you are running an ethanol blend. with a 91 octane tune with e10 91 in the car it would not go over 3700 rpms without pinging/knocking horribly, same tune with 100% gasoline and the car runs like a dream.