E85 vs Regular Gas Calculator

About the E85 vs Regular Gas Calculator

E85 (85% ethanol, 15% gasoline) is often priced lower than regular gasoline at the pump. However, E85 contains about 27% less energy per gallon, which means your vehicle gets significantly fewer miles per gallon when running E85. The real question is whether the lower pump price compensates for the reduced fuel economy.

This calculator compares the cost per mile of E85 versus regular gasoline by factoring in both the fuel price and the MPG difference. For flex-fuel vehicles that can run either fuel, this tells you which option actually saves money.

Typically, E85 needs to be priced at least 20–30% below regular gas to break even. In some states with ethanol subsidies, E85 is cheap enough to save money; in others, regular gas wins on a per-mile basis.

Accurate E85-versus-regular figures help you compare local fuel-price scenarios and avoid costly surprises at the pump.

When This Page Helps

Pump price alone is misleading for E85. Because E85 delivers fewer miles per gallon, you need to compare cost per mile, not cost per gallon. This calculator does that comparison accurately so flex-fuel vehicle owners can make the right fueling choice.

How to Use the Inputs

1. Enter the E85 price per gallon.
2. Enter the regular gas price per gallon.
3. Enter your vehicle's MPG on regular gas.
4. The calculator estimates E85 MPG (typically 73–80% of regular MPG).
5. Compare the cost per mile for each fuel.
6. See the annual cost difference based on your driving miles.

Example Calculation

Tips & Best Practices

• E85 typically delivers 20–27% fewer MPG than regular gasoline.
• E85 must be priced ~25% below regular gas to break even on cost per mile.
• Only flex-fuel vehicles (FFVs) should use E85 — check for the yellow gas cap.
• E85 prices vary wildly by region; Midwest states often have the best deals.
• Track your actual E85 MPG; some vehicles lose less efficiency than others.
• E85 has a higher octane rating (100–105), which can benefit performance-tuned vehicles.

Understanding E85 Energy Content

E85 contains about 73–83% of the energy in a gallon of regular gasoline. This is because ethanol has an energy density of 76,330 BTU/gallon versus 114,000 BTU/gallon for gasoline. The blended E85 result is approximately 83,000 BTU/gallon.

Regional Price Differences

E85 pricing varies dramatically. In Iowa, Kansas, and Minnesota, E85 can be $0.60–$1.00/gallon cheaper than regular gas, often making it cost-effective. In California, New York, and Florida, the discount is typically $0.30–$0.50, which rarely beats regular on a per-mile basis.

Performance Benefits

E85 has an octane rating of 100–105, much higher than regular gas (87) or premium (93). Performance-modified vehicles can take advantage of this higher octane for more aggressive ignition timing and boost, potentially improving power output significantly.

The Flex-Fuel Advantage

Flex-fuel vehicle owners have the unique advantage of choosing their fuel based on the local prices they enter. Check E85 prices before each fill-up and choose the cheaper option on a per-mile basis. This flexibility can save $200–$400 per year in fuel costs in the right market.

Frequently Asked Questions

• How much MPG do I lose on E85?

  Most flex-fuel vehicles lose 20–27% of their gasoline MPG when running E85. A car rated 28 MPG on regular gas will typically get 20–22 MPG on E85. The exact loss depends on the engine's ability to adapt its timing and fueling.

• Is E85 bad for my engine?

  In flex-fuel vehicles, E85 is perfectly safe — they're designed for it with compatible fuel lines, seals, and engine management. In non-flex-fuel cars, E85 can damage fuel system components and should never be used.

• When does E85 actually save money?

  E85 saves money when its pump price is more than 25–30% below regular gas. For example, if regular is $3.50, E85 must be below about $2.45–$2.63 to be the cheaper choice on a per-mile basis. This happens mainly in Midwest corn belt states.

• Does E85 produce less CO₂?

  Ethanol is a renewable fuel, and lifecycle CO₂ analysis shows E85 produces about 15–25% less greenhouse gases than gasoline. However, this depends on corn farming practices and varies by study. The per-mile emissions are higher due to lower MPG.

• Can I mix E85 with regular gas?

  In flex-fuel vehicles, yes. The engine management system adjusts automatically to any blend. Mixing gives you intermediate performance and MPG. Many drivers fill half E85 and half regular for a balanced approach.

• Why is E85 so cheap in some areas?

  E85 prices are lowest in the Midwest where corn is abundant and ethanol plants are nearby. Federal and state ethanol subsidies and mandates also reduce costs. Coastal and southern states have higher E85 prices due to transportation costs.