what kind of gas

my dad has a 04 gto 6 speed and I beleive they take higher octane gas. He was telling me that he "hiballs it" meaning that he uses half a tank of mid grade and a hald of high grade gas. Is this bad for the engin? I'm guessing yes, but what do I know

At 10.1:1 (static compression), it really should have at least a steady diet of 92 octane. 93 would be better... That being said, it the power is there, and there are no signs of detonation with the 89/93 mix, go ahead. It isn't hurting anything. You may be giving up a bit of top-end power, as the computer "manages" the detonation by retarding timing and richening the mixture.

My dealer said you can use mid grade 89 Octane. If the engine begins to ping, then he said to go back to high octane.A s the other poster said you may lose some grunt.

I would just always run premium. It's worth the extra money to make sure you're always feedin it the right stuff to ensure minimal KR. It's reccomended for that fuel, so I would run it in it all the time.