Onetogofast

iTrader: (9)

Tow rig, 07 Yukon Denali w/ 6.2L. Load, 3,500# boat. The first part of the trip I was running 93 octane ethanol fuel averaging 9.9-10. mpg. I stopped and filled up from 3/8 of a tank with 87 octane pure-gas non ethanol and was averaging 9.5 mpg on the dot. My question is, does the octane/ethanol change sound correct for MPG change? Denton, TX 93 octane was $3.90/gal and the 87 octane pure-gas was $3.44/gal. The pure-gas at this station in Witchita Falls had some major price jumps in octane levels, it jumped $3.44, $4.01, $4.51. I was shocked it jumped more than a dollar but it was 93 octane there as well. Let me know what you guys think of the pure-gas low octane running against ethanol high octane.

sprayedenali

iTrader: (11)

ig their octane rating is correct than the fuel with ethanol wouldnt necessarily give you any more power than if it were 100% gasoline. but there will be a mileage difference. so if you can get 93 in 100% gas or 90% gas/10% ethanol then the gas will give you the same power and better mileage...

Fasglas

Since it sounds like you changed to the 100% gasoline on the second leg of a road trip there's no telling what really happened because you weren't traveling over the same section of road with the same weather and temps with each tank of gas.

On a road trip from Los Angeles to Oklahoma every time I filled up I got different gas mileage because each tank of gas was over different terrain with different temps and weather.