I am not sure why, but I have had a lot of people ask me recently about flex fuel vehicles, what they are, and if they should use E85, since it is cheaper than gasoline.
Flexible fuel vehicles (FFVs) are designed to run on gasoline or gasoline-ethanol blends of up to 85% ethanol (E85). Except for a few engine and fuel system modifications, they are identical to gasoline-only models. FFVs experience no loss in performance when operating on E85, and some generate more torque and horsepower than when operating on gasoline. However, since ethanol contains less energy per volume than gasoline, FFVs typically get about 20-30% fewer miles per gallon when fueled with E85, thus wiping out any savings per gallon, and will cause you to go to the pump more often.
The EPA tracks fuel economy for all sorts of vehicles at its website, FuelEconomy.gov, including flex fuel vehicles. I looked at a 2017 Chevy Tahoe with the 5.3-liter V8. Running on regular fuel, the fuel economy rating is 19 combined city and highway. On E85, that drops to 14 combined. The range on a tank of regular fuel is 494 miles, using the flex fuel option it drops to 364 miles.
Putting a dollar amount to it, in Dallas where I am located, regular fuel today is $2.16 per gallon. E85, when found, is $1.73. Using our handy fuel calculator from CarProUSA.com. I quickly calculated that for a 15,000 mile per year driver in the Tahoe, the annual cost for regular fuel is $1705. With E85, even with the decreased per gallon cost, you will spend $1853 per year, resulting in a net increase of roughly $150 per year.