What Happens When You Put Diesel in a Gas Engine?

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A woman putting diesel in her gas engine by accident

Ever wondered what happens when you put diesel in a gas engine? While we’re not mechanics, we can tell you with confidence that you’ll likely be talking to one soon after putting diesel in your gas tank.

Mistakes happen, and we want to help you not only avoid making a mistake but know what to do if you accidentally fill up with diesel instead of gas. So let’s get started!

A gas pump at a gas station to fill up a gas tank. Drivers are able to pick three different options to put into their tank and it is important drivers understand what happens when putting diesel in gas engine will do to to a car.

What’s the Difference Between Gas and Diesel?

You may pull up to a gas pump that has both diesel and gasoline fuel pump nozzles. Depending on the fuel station, they typically use green pump handles to indicate diesel and black pump handles for gasoline. However, the difference between the two fuels is more than just the color of the pump handle.

Diesel is a thicker fuel, denser energy, and resistant to evaporation. It’s more efficient, and drivers usually experience much better fuel economy. Both gasoline and diesel fuels contain chemical energy. They differ most in how engines convert them from chemical energy into mechanical energy.

Gasoline engines use a spark plug to ignite the gasoline, and diesel engines use compression to create explosions inside the engine to keep the pistons moving.

Pro Tip: On a budget? Learn how to save money on your RV road trip.

A fuel gauge showing a full tank of gas. Drivers should know the difference between what type of gas is correct for their vehicle and what happens when you put diesel in a gas engine.

Can You Put Diesel in a Gas Engine?

No, you should not ever put diesel into a gas engine. What happens when you put diesel in a gas engine is it changes the octane level of the fuel in your fuel system. This can cause several issues with your vehicle, and it may create a massive amount of visible smoke from your exhaust.

If you continue to drive, it will most likely result in your vehicle shutting down. You’ll then need to call a tow truck and have it towed to a local mechanic. 

Keep in Mind: Do you know the do’s and don’ts of filling up at a truck stop? Read this article to see if RVs can use truck stop fuel pumps.

What Happens When You Put Diesel in a Gas Engine?

When diesel fuel enters your gas engine’s fuel system, a few things are likely to happen. So let’s look at what exactly happens and causes issues if this happens to you.

Fuel Pump Issues

Diesel is too thick for a gasoline fuel pump to handle. The fuel pump will struggle to move the more viscous mixture through your vehicle’s fuel system. This will cause a tremendous amount of strain and potentially a significant failure of your fueling pump if there are any pre-existing conditions or nearing the end of its lifespan.

Clogged Fuel Filter 

Because diesel is thicker, it won’t be able to pass through your fuel system’s fuel filter as quickly as gasoline. The oily diesel fuel will likely instantly clog your fuel filter and cause your system to struggle.

Clogged Fuel Injectors

Any diesel fuel that passes through the fuel filter will clog your vehicles’ fuel injectors. Ultimately this will result in your vehicle shutting down and becoming inoperable.

You may be able to travel for a little bit as your vehicle burns through the gasoline that’s in the fuel system. However, it’s only a matter of time before the diesel clogs the injectors, and you have to call a tow truck.

What Should I Do If I Accidentally Put Diesel in My Car?

Mistakes happen, and if you accidentally put diesel in your car, how you immediately respond can determine what you will need to fix the situation. Here’s how you should react no matter when you catch the mistake.

A guy filling up his vehicle with the appropriate gas for his engine, as they know what happens when you put diesel in a gas engine.

Don’t Start the Vehicle (Or Shut Off the Vehicle ASAP)

The best bet is that you catch the mistake before starting the vehicle. Not starting the vehicle will keep the diesel fuel in your fuel tank and limit damage to your fuel pump, fuel filter, and fuel injectors.

If you don’t catch the mistake until you notice the smoke or after starting the engine, turn off the vehicle as soon as possible. Find a safe place to pull over and park, and call someone to give you a ride.

Call a Tow Truck

Continuing to drive the vehicle or run the engine will worsen the issue. Call a tow truck and get a tow. This will limit the amount of damage and give you the best chance at minimizing your future repair bill.

If your vehicle’s insurance policy includes emergency roadside assistance, you may want to give them a call and let them reach out to an approved tow truck company. Depending on where you need to tow your vehicle, you may not need to pay anything to have your vehicle towed.

Get to a Mechanic

You’ll want to get your vehicle to a mechanic as soon as possible. You’re not the first person to make this mistake. This isn’t an uncommon situation, and many mechanics are well-equipped to address the problem. It likely will cost more than you expect, however.

A mechanic working to fix a car engine, a common occurrence as some are unsure of what happens when you put diesel in a gas engine.

How Much Does It Cost to Flush Diesel Out Of a Car? 

If you put diesel in a gas engine, you’ll need to get the diesel out of your vehicle. Costs may vary from one shop to another, but the repair can cost upwards of $2500. Draining your vehicle’s fuel tank can cost anywhere from $200 to $500, and if the fuel enters your fuel lines or engine, the costs jump quickly into the ballpark of $1,500 to $2,500.

This is a pretty hefty repair bill. You’ll want to give your insurance company a call and see if you can make an insurance claim for the repairs.

Most insurance policies will not protect drivers from expenses due to misfuelling. However, only your insurance provider can speak to the coverages and any limitations on your policy.

Double Check Your Pump at the Station

Now that you know what happens when you put diesel in a gas engine, you know a simple mistake can result in a significant hit on your bank account. We encourage you to check the pump twice at the fuel station. You can save yourself the stress and financial impact if you do.

Have you ever made the mistake of putting the wrong fuel into your tank?

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