Ethanol Fuel Consumption Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026Ethanol Fuel Consumption Calculator
Ethanol contains roughly 34% less energy per gallon than pure gasoline - this calculator adjusts a vehicle's gasoline-equivalent fuel economy rating to account for the real-world impact of running on an ethanol-blended fuel.
Formula
Effective MPG = Gasoline-Equivalent MPG / (1 + Blend% x 0.34)
Gallons Needed = Distance / Effective MPG
Example
A vehicle rated at 30 MPG on gasoline, running E85 (85% ethanol) for a 300-mile trip:
Effective MPG = 30 / (1 + 0.85 x 0.34) ≈ 23.3 MPG → Gallons Needed ≈ 12.89
Why E85 Fuel Economy Drops So Much
Flex-fuel vehicles running E85 typically see noticeably lower miles-per-gallon than the same vehicle running standard gasoline or low-blend E10, purely due to ethanol's lower energy density - this is why E85's often-lower price per gallon at the pump doesn't automatically translate into lower total fuel cost per mile driven; the true cost comparison needs to account for this energy content penalty.