Young woman standing outside putting gas in her car.

What to do if you put the wrong fuel in a car

Let the engine, not the dollar signs, guide you.

Price can be a pretty big influencer when it comes to filling your car. But choosing a type of fuel on cents alone may be a costly mistake. Here's what could happen if you put the wrong fuel in your car.

Diesel fuel in a gas tank

How it can happen: This is hard to do — but not impossible. Diesel pumps are typically a different color and have larger nozzles that usually won't fit into a gasoline tank's opening.

What to do: Gas engines can't combust diesel, so your car may not start; if it does, it will probably smoke. While engine damage is unlikely, you will need to get the tank drained, a service that may range from $500 to $1000, and pay for the cost of a tow.

Gas in diesel

How it can happen: Gas nozzles are smaller, so they could fit into a diesel engine tank. If this happens, know that the engine can react by simply turning the key, so try to recognize the mistake before you start the car.

What to do: Because diesel acts as a lubricant for the fuel system, thinner gasoline can cause the fuel pump, filter, and injectors to wear, especially if the engine runs. Call for a tow and have the tank drained and the parts checked.

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Plus/premium in regular gas

How it can happen: This is mostly a matter of choice or preference; always refer to your owner's manual for fuel-type recommendations.

What to do: Nothing. You probably won't see any benefits or damage.

Regular in plus/premium

How it can happen: Again, this is mostly a matter of choice or preference.

What to do: You may hear rattling and notice reduced performance and decreased fuel economy, but your car probably won't sustain lasting engine damage. Simply switch back to premium as soon as possible, and always refer to your owner's manual for recommendations.

Ethanol E85 in gas

How it can happen: Ethanol should be clearly labeled at the pump, but grabbing the wrong nozzle can happen.

What to do: If the car is not a flexible-fuel vehicle, you may see the "check engine" light flicker — and this may void the manufacturer warranty. However, this swap probably won't cause permanent damage. Keep topping off your tank with regular gasoline; your car should eventually run as normal.

How to prevent choosing the wrong fuel

  • Know your car: Diesel vehicles can use diesel, and that's it. For gasoline cars, check your owner's manual for the minimum octane rating, and make sure the fuel equals or exceeds that number. Generally, regular has an octane level of 87, premium is 91 or 93, and plus falls somewhere in between. Cars that require premium also may specify an octane preference on the gas cap. (Some cars may simply "recommend" a fuel.)
  • Consider a mis-fueling prevention device: You can purchase a diesel fuel tank insert that refuses gas nozzles. Some car manufacturers have started equipping all diesel vehicles with a similar mechanism as a standard.
  • Pay attention at the pump: Eliminate distraction at the pump (leave your phone in the car, for example). Carefully review each button and/or nozzle to make sure you know which fuel type you are choosing.

Does insurance cover putting wrong fuel in?

If you've merely added plus/premium to a regular tank or vice versa, you won't suffer any financial costs. But if you need a tank drain or tow, you'll need to check with a State Farm® agent to see if your insurance covers the damage. Most insurance policies do not cover misfueling but some offer specialty riders that do.

Here are some ideas to use less gas, what to do if your gas pedal sticks and ways to protect your vehicle from gas theft.

The information in this article was obtained from various sources not associated with State Farm® (including State Farm Mutual Automobile Insurance Company and its subsidiaries and affiliates). While we believe it to be reliable and accurate, we do not warrant the accuracy or reliability of the information. State Farm is not responsible for, and does not endorse or approve, either implicitly or explicitly, the content of any third party sites that might be hyperlinked from this page. The information is not intended to replace manuals, instructions or information provided by a manufacturer or the advice of a qualified professional, or to affect coverage under any applicable insurance policy. These suggestions are not a complete list of every loss control measure. State Farm makes no guarantees of results from use of this information.

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