E85 vs 91 for street

my68barracuda said

just wondering, with today’s vehicles that are Flex Fuel capable, I have read more than once that the fuel mileage really goes down when running E85 compared to regular gas.
Wonder how much of that mileage loss is because the Flex Fuel motor is not compensating for the higher compression that E85 is capable of running when compared to regular gas?

Click to expand...

Yes mileage suffers but at least arounf here, E85 is a quite a bit cheaper than 87oct and a LOT cheaper than 93oct, so its either saving money or a wash.

New flex fuel cars are typically over 10.1 compression(some over 12.1) and use variable valve timing in take advantage of the higher octane of E85. The PCM calibration is smart enough to know how much Ethanol is being used and adjust the cam timing and ignition timing accordingly.