It is safe to say that when you run higher octane fuel, you will get worse gas mileage (unless you have a tune other than stock).

Further, I feel ya on the bad gas mileage - my 97 GTP only gets about 21-23 MPG mixed city and hwy driving. It would be nice to get the 25-26 MPG like the other fellas on here.... but I'm working on that.

Good Luck!

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Former Camaro muscle and DSM turbo owner - now moving into the GTP Supercharged world!

1997 GTP - STOCK.... for now