How do I know if my vehicle is E85 compatible?

Only flex-fuel vehicles (FFVs) are truly E85-compatible; non-FFVs should not use E85 unless the manual says otherwise.

In practice, E85 compatibility means the engine and fuel system are designed to safely operate with ethanol blends up to 85 percent. Vehicles that can use E85 are typically labeled "Flex Fuel" or "FFV" and documented in the owner's manual or on the VIN/window sticker. If it's not labeled or documented as such, treat it as gasoline-only.

Understanding E85 and FFVs

What is E85?

E85 is a gasoline-ethanol blend containing up to 85% ethanol. The exact blend in a given tank can vary by season, region, and fuel supply, so vehicles that are not FFV should not expect to run on E85 reliably.

What is a Flex-Fuel Vehicle (FFV)?

An FFV is designed to tolerate ethanol-rich fuels. It uses materials and an engine management system compatible with ethanol blends. If your vehicle is FFV, it can run on E85, gasoline, or any blend in between (such as E10, E15, E30, E50, etc., depending on design and calibration).

How to Confirm E85 Compatibility

To be certain, use these steps to verify whether your specific vehicle can use E85 without risk.

• Check the owner's manual for mentions of "Flex Fuel," "E85," or "FFV."


• Inspect the fuel filler door or near the fuel cap for labels like "E85" or "Flex Fuel."


• Look for FFV or Flex Fuel badges on the vehicle (rear bumper, trunk lid, or inside the fuel door).


• Confirm via the Vehicle Identification Number (VIN) with the dealer or manufacturer; some brands provide FFV status in online portals.


• Review the window sticker (Monroney label for new cars) for "Flex Fuel" or "E85 capable."


• Consult the automaker's official website or customer service with model/year and VIN to confirm compatibility.

Following these steps will give you a reliable answer about E85 compatibility for your particular vehicle.

Practical considerations when using E85

Even when a vehicle is FFV, there are performance and maintenance considerations to keep in mind.

• E85 has lower energy content than gasoline, so expect lower fuel economy (roughly 25-30% less energy per gallon) and potentially reduced MPG in typical driving conditions.


• Modern FFVs are designed to handle ethanol, but older non-FFV systems can suffer rubber and seal degradation or fuel-system corrosion when exposed to high ethanol blends.


• Fuel system materials and sensors adapt to ethanol blends; cold-weather starting and power output can differ from gasoline-only operation, and the ECU adjusts fuel mix automatically in FFVs.


• Warranty coverage and regional fuel regulations can impact what you should run; always follow the manufacturer's recommendations for your vehicle.

In practice, FFVs offer flexibility, but the trade-off is typically lower energy density and, depending on the vehicle, variable efficiency gains or losses based on driving conditions and ethanol content.

What to Do If Your Vehicle Is Not FFV

If your car isn't FFV, you should not use E85. In most cases, your vehicle's fuel system isn't designed for high ethanol content, and using E85 can lead to fuel-system damage and warranty issues. If you want to use ethanol-blended fuels, consider lower-ethanol options such as E10 or E15 where supported by your vehicle and local regulations; always follow manufacturer recommendations.

Summary

The quickest way to know if your vehicle can use E85 is to look for FFV labeling, check the owner's manual, and verify via the VIN or window sticker with the dealer or manufacturer. If your car is not an FFV, do not use E85. If it is FFV, you can choose E85 or gasoline or any blend within the design limits, but expect some changes in fuel economy and performance.

How do I tell if my car can use E85?

Check Your Owner's Manual: The easiest way to determine if your car can use E85 is by consulting your vehicle's owner's manual and see what fuel is recommended.

Can you put E85 in any vehicle?

No, you cannot put E85 in any car; it is only safe for flex-fuel vehicles (FFVs) or cars that have been converted to run on it. Using E85 in a standard gasoline car can cause engine damage due to its high ethanol content and because the fuel system is not designed to handle it. You can identify a flex-fuel vehicle by checking for a yellow gas cap, an "E85" or "Flex Fuel" label, or the corresponding information in your owner's manual. 
This video explains the risks of putting E85 in a non-flex-fuel vehicle: 49sBo BuildsYouTube · Jun 22, 2019
Signs your car is flex-fuel compatible 

• A yellow gas cap
• A yellow ring around the gas cap opening
• A badge on the car that says "Flex Fuel," "FFV," or "E85"
• Information confirming compatibility in your owner's manual 

What happens if you use E85 in a non-flex-fuel vehicle

• Engine damage: The higher ethanol content can corrode or degrade parts not designed for it, such as fuel lines, gaskets, and seals. 
• Performance issues: Your car may run poorly, with symptoms like trouble starting, engine stumbling, misfires, and a loss of power. 
• Check engine light: Issues with the air-fuel ratio can cause the check engine light to come on. 
• Voided warranty: Using E85 in an incompatible vehicle can void the manufacturer's warranty. 

What to do if you accidentally put E85 in a non-flex-fuel car

• Do not start the engine repeatedly. This could cause more damage. 
• Have the fuel tank professionally drained and flushed. You can call a tow truck to take the vehicle to a service station for a fuel system flush. 

What happens if I put E85 in a car that doesn't take it?

Engine computers can usually adjust their timing to account for the increased octane levels, so if you put premium gas in a regular car, you probably won't notice anything. However, some engines are not designed to burn higher-octane fuel, and you may see a reduction in performance and fuel economy.

Is it okay to mix E85 and 87?

Yes, you can mix E85 and 87 octane gas, but only in a Flex Fuel Vehicle (FFV). Mixing E85 in a standard gasoline engine is not recommended as it can damage the fuel system, and the vehicle will likely run poorly, leading to issues like a check engine light, corrosion, or catalytic converter damage. 
For Flex Fuel Vehicles (FFVs)

• FFVs are designed to run on any blend of gasoline and ethanol, from pure gasoline to E85. 
• The vehicle's computer will automatically adjust to the ethanol content of the fuel mix. 
• You can mix E85 and 87 in any ratio you want; there is no need to worry about damage. 
• Expect slightly lower fuel mileage when using higher ethanol content, but the performance can sometimes increase. 

For Non-Flex Fuel Vehicles

• Do not mix them . 
• E85 is not compatible with a standard engine's fuel system and can cause damage. 
• Ethanol can corrode or deteriorate the rubber and plastic components in older fuel systems. 
• The vehicle's engine may run lean, causing knocking or pinging, and the check engine light may come on. 
• If you mistakenly put E85 in a non-Flex Fuel vehicle, it's best to drain the tank completely to avoid potential damage.