How much MPG do you lose on E85?

Roughly 25–30% versus E10 pump gas, because ethanol carries about a third less energy per gallon. E85 must be meaningfully cheaper per gallon to break even per mile.

What Is E85? Ethanol Flex Fuel Explained

Q: Is E85 actually 85% ethanol?

Rarely. Pump E85 legally ranges from 51% to 83% ethanol depending on season and region; winter blends run leaner for cold starts. Test it if your tune depends on it.

Q: Does E85 make more power?

On an engine tuned for it, yes: E85's knock resistance lets tuners run more ignition timing and boost, and its charge-cooling effect helps further. On an untuned flex-fuel vehicle the gain is usually small.

E85 is a motor fuel made of ethanol blended with gasoline: nominally 85% ethanol, legally anywhere from 51% to 83% at the pump depending on season. It's sold at the yellow-badged pump, usually well below the price of regular.

WHY ENGINES LOVE IT

Ethanol resists knock far better than gasoline; E85 behaves like 100–105 octane race gas at a fraction of the price. It also cools the intake charge as it vaporizes. Together that lets a tuned engine run more ignition timing and more boost safely. That's why E85 owns the budget end of drag strips and dyno queues: it's the cheapest horsepower per dollar in fueling.

THE CATCH: ENERGY PER GALLON

Ethanol carries about a third less energy per gallon than gasoline, so expect roughly 25–30% fewer miles per tank on E85 versus E10 pump gas. Cheaper per gallon doesn't automatically mean cheaper per mile. Run your local prices through our break-even calculator to see which side of the line you're on.

WHO CAN RUN IT

Factory flex-fuel vehicles (FFVs): millions of trucks, SUVs and sedans shipped E85-ready. Check your exact model and engine here.
Tuned non-flex cars: with a proper tune, bigger injectors, and an adequate pump, most modern EFI engines convert well. See the conversion guide.
Blenders: you don't have to run full E85. Mixing E85 with pump gas to hit E30 or E50 captures most of the benefit with less of the drawback. That's exactly what the blend calculator is for.

THE HONEST SUMMARY

Run E85 (or a blend) for octane, cooling, and power headroom. Treat any per-mile savings as a bonus: some weeks it's real, some weeks it isn't, and the math takes ten seconds.

FAQ

Is E85 actually 85% ethanol?

Rarely. Pump E85 legally ranges from 51% to 83% ethanol; winter blends run leaner for cold starts. If your tune depends on the number, test it.

Does E85 make more power?

On an engine tuned for it, yes: more timing and boost, plus charge cooling. On an untuned FFV, the gain is small.

How much MPG do you lose?

Roughly 25–30% versus E10. Blends lose proportionally less; E30 costs you about 7%.

WHAT IS E85?