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?