Quote Originally Posted by kitz
I have heard of it before and I believe it's possible to get better gas mileage using the more expensive (higher octane) gas. I think the cheapy unleaded regular causes the ECU to richen the fuel slighlty due to feadback within the EFI system (knock sensors, O2, etc.). Actual results may vary.

Kitz
I wont use the more expensive gas at 30 to 40 cents more for 2 octane points(up to 89) or 50-70 cents more for the 93 for an experiment. My truck was built for the 87 gasoline which means the ECU is programmed for that stuff. I'll get a reflash of the ECU in a couple of months for any updates. On my Ford truck forums there have been threads on lower gas mileage with the 90/10 gas to ethanol blends but I haven't found an reputable on-line article about this yet. It does make sense that there will be a difference in combustion flame propagation in the engine. This propagation has to be modified by this amount of a volitile additive, 10%. I just am not sure which way. Unfortunately I just don't have enough information one way or the other to understand this.