[Nukedog]

Lots of (bad) info in this thread and very little good. Not much can be proven without a dyno and someone who can alter timing on this engine. You CAN get a difference in mileage (not related to octane rating) by using better quality gas. I have verified over and over that i consistently get the best gas mileage from Chevron and get worse mileage from Hess. Like someone said before you can google the "octane myth" and learn something. These motors are 10.2 CR so they are relatively high for a everyday usage engine so they may very well benefit from 89/91 or even 93. They also may not and they certainly will get less mileage with E10 as compared to regular petrol...