Frequent Questions | Green Vehicle Guide | US EPA
Why is the fuel economy for a flex-fuel vehicle lower when using E85 than when using gasoline?
Ethanol has a lower energy content than gasoline as measured in British Thermal Units per gallon, so you travel fewer miles per gallon when using a fuel that contains ethanol. Compared to gasoline, E85 typically gets about 25-30 percent fewer miles per gallon in ethanol flexible fuel vehicles.