What to Do If You Put Diesel In a Gas Engine

diesel gas engine

You pull your car up to the pumping station or perhaps you’re driving your boat to a marine fuel dock. Did you accidentally put diesel fuel in your car’s gas tank or gasoline fuel in your boats diesel fuel tank? Do you know what to do next without causing injury to yourself or damaging your motor vehicle further? Learn more about diesel fuel, gasoline fuel and what to do if you put diesel in a gas engine.

What Happens If You Put Diesel in a Gas Engine?

Gasoline requires an octane rating of 87-91, the variance is because of  fuel grade. According to the U.S. Department of Energy, “Octane rating is the measure of a fuel’s ability to resist “knocking” or “pinging” during combustion, caused by the air/fuel mixture detonating prematurely in the engine.” It has to ignite at just the right time to be efficient.

Since diesel fuel has an octane rating of 25-30, pumping diesel fuel into a gas tank can lower the octane level needed and cause damage to the gas engine. The more diesel fuel pumped into the gas tank, the higher the level of diesel contamination. All of this can cause significant damage to the engine and interconnected parts that work together to make your car go.

What to Do If You Put Diesel in a Gas Engine

Don’t panic. The fact that you put diesel fuel in a gas engine is far better than pumping gasoline fuel into a diesel engine, which can be far more dangerous.

Let’s say you accidentally fill your gas tank up with 50% of diesel. It’s quite possible your car will not start and you will have to it towed to a garage to have the tank drained.

Here is what you should do:


  • Approximate how much diesel was pumped into the gas tank. It’s helpful to know if you only pumped in a drop or 50% of the tank is now full with diesel fuel. 
  • Do not attempt to operate the vehicle. Minimize your risk of costly repairs by not running the vehicle. By not operating the vehicle you are avoiding the possibility of sucking up diesel into the fuel line. If you attempt to drive the vehicle with diesel in the engine, your engine could seize and may require extensive repairs as a result. Also, this requires immediate attention. Leaving diesel fuel to sit for too long can cause further damage. 
  • Call a garage. Contact a local garage you trust and explain the situation. They will most likely recommend draining your gas tank. Make arrangements with the garage so that when the tow truck arrives, the tow truck can directly deliver the vehicle to the garage.  
  • Call a tow truck. As soon as you hang up with the garage, reach out to a tow truck company to have your vehicle towed to the garage.

What is the Difference Between Gasoline Fuel and Diesel Fuel?

Diesel fuel: Diesel fuel is specifically designed to work with diesel engines and can be found most commonly in diesel engine motor vehicles.  Examples of diesel engine motor vehicles include: eighteen wheelers, trains, buses, boats etc. Diesel is also a type of distillate fuel produced from crude oil.

Gasoline Fuel: Like diesel, gasoline fuel is made from crude oil,  but has slightly different additives that change its makeup. Most often gasoline fuel is mixed with ethanol. According to the U.S. Energy Information Administration (eia), “Most of the motor gasoline now sold in the United States contains about 10% fuel ethanol by volume.”

The Difference in Gasoline Fuel v. Diesel Fuel

  1. Diesel fuel is heavier than gasoline (larger molecules).
  2. Diesel fuel maintains a different density and viscosity than gasoline.
  3. Diesel fuel has a lower autoignition temperature than gasoline.

Something else worth nothing is that diesel engines do not have spark plugs — they just aren’t required to ignite the engine.

If you’re interested in sharpening your knowledge and becoming a more proactive driver, contact Top Driver today to sign up for an online refresher driving course. Many car insurance providers offer discounts for completion of proactive driving courses, so be sure to ask your insurance provider for more information and ways to save!

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