Can You Use E85 Gas in a Regular Car?

You should not use E85 gas in a regular gasoline-powered car unless the manufacturer specifically approves it. E85 is intended for flexible-fuel vehicles, commonly called flex-fuel vehicles or FFVs. These vehicles are designed to operate on regular gasoline, E85, or a mixture of the two.

E85 sometimes costs considerably less per gallon than regular unleaded gasoline, making it tempting when you’re trying to save money at the pump. However, using it in a vehicle that isn’t designed for high ethanol concentrations can cause engine performance problems and potentially damage fuel-system components. Even in a compatible vehicle, the lower price doesn’t always translate into lower driving costs.

What Is E85 Gasoline?

E85 is a blend of gasoline and ethanol, an alcohol-based fuel commonly produced from corn and other plant materials. Despite its name, E85 doesn’t always contain exactly 85% ethanol.

According to the U.S. Department of Energy’s Alternative Fuels Data Center, E85 sold in the United States typically contains between 51% and 83% ethanol. The percentage changes with the season and geographic location, partly to help vehicles start reliably in colder weather.

Regular gasoline often contains ethanol too, but at much lower concentrations. The common E10 blend contains up to 10% ethanol, while E15 contains approximately 15%.

These distinctions matter because a car that can use E10 or E15 isn’t automatically compatible with E85.

How Do You Know If Your Car Can Use E85?

The most reliable way to determine whether your vehicle can use E85 is to check your owner’s manual or the manufacturer’s fuel requirements. Look for language identifying the vehicle as a flexible-fuel vehicle or stating that it can use E85.

Other possible indicators include:

• A yellow gas cap: Many flex-fuel vehicles have a yellow fuel cap, although not every compatible vehicle uses one.
• Labels near the fuel filler: You might see an E85 or Flex Fuel label on the fuel door or near the filler opening.
• Exterior badges: Some manufacturers identify flex-fuel models with an emblem or badge on the vehicle.
• Vehicle specifications: The manufacturer’s documentation or an official vehicle lookup can confirm whether your particular model and engine are compatible.

Don’t rely exclusively on a badge or fuel cap, particularly if you’re driving a used vehicle that may have replacement parts. Some flex-fuel vehicles have no obvious exterior markings.

The Department of Energy explains the differences between conventional gasoline vehicles and flexible-fuel vehicles, including their ability to operate on gasoline and high-ethanol blends.

What Happens If You Put E85 in a Car That Isn’t Flex Fuel?

Putting E85 into a vehicle that isn’t designed for it can create several problems. The severity depends on the vehicle, how much E85 was added, whether the engine has been operated, and the fuel-system components involved.

Engine Performance Problems

Engines designed for ordinary gasoline aren’t necessarily calibrated to handle the high ethanol content of E85. Ethanol requires a different fuel-to-air mixture than gasoline, and a conventional engine’s fuel system may be unable to deliver the amount needed.

Possible symptoms include difficulty starting, rough idling, hesitation, loss of power, and an illuminated check-engine light. Some vehicles may experience more serious running problems.

These symptoms aren’t guaranteed after every accidental fill-up, but the absence of immediate problems doesn’t mean the fuel is appropriate for your vehicle.

Potential Fuel-System Damage

Flex-fuel vehicles have components and engine controls designed to accommodate ethanol’s different chemical properties.

The Department of Energy explains that these vehicles use ethanol-compatible fuel-system components, including modifications to the fuel pump and fuel injection system, along with engine-control calibrations suited to high ethanol concentrations.

Some conventional vehicles have seals, hoses, pumps, or other components that aren’t designed for prolonged exposure to high-ethanol fuel. Incompatible materials and operating conditions can contribute to deterioration or malfunction.

However, E85 doesn’t automatically destroy every rubber component it touches, and a single accidental fill-up doesn’t necessarily mean thousands of dollars in repairs. The risk depends on the particular vehicle and circumstances.

Reduced Fuel Economy

E85 also contains less energy per gallon than conventional gasoline. That means even a vehicle specifically designed for E85 generally travels fewer miles on a gallon of fuel.

According to the U.S. Department of Energy, E85 containing 83% ethanol has approximately 27% less energy per gallon than gasoline. Actual fuel economy varies depending on the ethanol percentage, vehicle, and driving conditions.

This reduction is an important consideration when comparing E85 prices with regular gasoline.

Is E85 Actually Cheaper Than Regular Gas?

E85 may have a lower price per gallon, but the more useful comparison is how much you pay to drive the same distance.

For example, suppose a flex-fuel vehicle gets 30 miles per gallon on gasoline and 23 miles per gallon on E85. Assume regular gas costs $3.50 per gallon and E85 costs $2.70 per gallon.

• Regular gasoline: $3.50 divided by 30 mpg = approximately 11.7 cents per mile.
• E85: $2.70 divided by 23 mpg = approximately 11.7 cents per mile.

In this hypothetical example, the two fuels cost almost exactly the same amount per mile, despite E85 being 80 cents cheaper per gallon. These are assumed prices and fuel economy figures for demonstrating the calculation, not verified market prices or guaranteed results for a particular vehicle.

To compare the fuels for your own flex-fuel vehicle, divide each fuel’s price per gallon by the miles per gallon your vehicle achieves using that fuel. Whichever produces the lower cost per mile is generally the less expensive option for fuel spending.

You can also check your vehicle’s gasoline and E85 fuel economy estimates using the U.S. Department of Energy’s FuelEconomy.gov website.

Can You Mix E85 With Regular Gas?

Yes, if your vehicle is designed for flex fuel. A flex-fuel vehicle can use regular gasoline, E85, or different mixtures of the two without requiring you to empty the tank between fuels.

For a vehicle that isn’t flex-fuel compatible, adding regular gasoline to E85 doesn’t automatically make the mixture safe.

For example, mixing equal amounts of E85 containing 83% ethanol and ordinary E10 gasoline would produce a fuel containing approximately 46.5% ethanol. That’s far above the ethanol content approved for typical non-flex-fuel vehicles.

If you’re trying to save money by adding a little E85 to your regular gasoline, check your manufacturer’s fuel requirements instead. Don’t assume that an intermediate ethanol concentration is acceptable simply because you’ve diluted it.

Is E15 the Same as E85?

No. E15 contains substantially less ethanol than E85, and different vehicle compatibility rules apply.

The Environmental Protection Agency permits E15 in model year 2001 and newer conventional passenger cars, light-duty trucks, and medium-duty passenger vehicles, as well as flex-fuel vehicles.

E15 isn’t approved for model year 2000 and older conventional vehicles, motorcycles, boats, lawn equipment, and certain other engines. Always check the manufacturer’s fuel specifications before choosing an ethanol blend.

Importantly, the fact that your car can use E15 does not mean it can use E85. The much higher ethanol content of E85 requires a vehicle designed for flex-fuel operation.

What Should You Do If You Accidentally Put E85 in Your Car?

If you’ve accidentally filled a non-flex-fuel vehicle with E85, the safest response depends on whether you’ve started the engine and how much of the incorrect fuel was added.

If you haven’t started the engine: Leave it off and contact your vehicle manufacturer’s service department or a qualified mechanic. Explain how much E85 you added and approximately how much gasoline was already in the tank. They can advise whether the fuel needs to be removed before operating the vehicle.

If you’ve already driven the vehicle: Stop in a safe location if you notice rough running, loss of power, warning lights, or other unusual behavior. Arrange for professional advice or roadside assistance rather than continuing to drive and hoping the problem resolves itself.

Even if the vehicle seems to run normally, contact a qualified technician for guidance before continuing to use the fuel. A professional can assess the risk for your particular make and model.

Don’t attempt to siphon fuel yourself. Gasoline and ethanol-gasoline mixtures are flammable, and draining a fuel system requires appropriate equipment and safety procedures.

Should You Choose E85 to Save Money?

If you own a flex-fuel vehicle, E85 is a legitimate fuel option worth comparing with regular gasoline. Check the price per gallon, consider the difference in fuel economy, and calculate your expected cost per mile. Depending on local prices and your vehicle’s efficiency, E85 may save money, cost about the same, or cost more.

If your car is designed only for conventional gasoline, however, the potential savings aren’t worth the compatibility risks. Stick to the fuel types approved by your manufacturer, even when the price displayed at the E85 pump looks appealing.