What Happens if You Put the Wrong Fuel In Your Car?

Whether you put diesel in a gas-powered engine or just used the wrong octane level, there could be danger. Learn what happens when you use the wrong gas.
Written by Jacoba Bood
Reviewed by Kathleen Flear
Putting the wrong fuel in a gas car is unlikely to cause serious damage. However, it’s usually worse to put gas in a diesel engine than to put diesel in a gas engine. Likewise, it’s more serious to put regular fuel in a car that takes premium fuel than vice versa.
The results of the error will vary on a case-by-case basis, but knowing what kind of fuel you added can help you take the right course of action to minimize the damage.
It might feel embarrassing, but using the wrong type of fuel is a common mistake—and mistakes happen.
The important thing is that you take steps to correct the error as soon as you can. To help you through it,
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What happens if I put the wrong fuel in my gas car?

Putting the wrong fuel in a gas car is unlikely to cause serious damage, but you could still get stuck with some costly repairs.
Diesel is more likely to cause damage
in a gas engine than E85, which may not affect the car at all.


The damage caused by using diesel in a gas engine isn’t usually permanent but could easily cost between $500 to $1000 in repairs.
There’s also a good chance that you’ll need a tow to the nearest mechanic. This might be covered if you have
roadside assistance
on your policy or
AAA membership
Gas and diesel have different nozzles, so it’s usually pretty tricky to mix them up at the pump. It can and does happen, though. The sooner that you can turn off the engine, the more likely it is that you’ll minimize the damage. Gas engines can’t process diesel, so your car will shut down on its own once the gas burns out—but that’s not ideal.
If you realize that you put diesel in your gas tank, pull over and shut down the engine as soon as you can. Once stopped, reach out to a mechanic who can drain your fuel lines.


Flex-fuel or FFV cars can switch between regular fuel and higher ethanol E85 fuel with no issues. Even if your vehicle doesn’t have a flex-fuel tank, E85 fuel is unlikely to cause any serious damage.
If you put E85 in your tank, you should be able to top it off with regular gas and ride it out.—just fill the tank a couple more times before you burn off the remaining fuel. If you notice any issues when driving, be sure to call up a professional mechanic right away.
Key Takeaway If you put diesel or E85 in your gas tank, your car might need repairs—but it’s unlikely to cause any serious or lasting damage.

What happens if you put gas in a diesel engine?

If you think you might have added gas to your diesel car, pull over immediately and shut off the engine. You’ll have to
arrange for a tow
to get your vehicle to a mechanic. The extent of the repairs will vary, but they could be costly depending on the damage.
Gasoline is more combustible in a diesel engine than diesel in a gas engine, meaning there is more potential for
engine damage
. Gas also lacks the lubricating properties of diesel and can damage the fuel pump when it cycles through.

What happens if I use the wrong grade of fuel in my gas car?

Depending on the circumstances, there could be no damage or there could be more serious internal damage. It mostly depends on the direction of the mix-up.
Premium fuel has a
low octane rating
and won’t damage a car that doesn’t need premium. But using regular fuel in a car that required premium could cause damage.

I accidentally put premium gas in my car. Now what?

Nothing will happen if you
put premium fuel in a car
that doesn’t require it.
Engine computers automatically adjust for octane, so you shouldn’t notice any difference in performance—for better or for worse. The only downside is the extra money you spent at the pump.

I put regular gas in a car that needs premium fuel

Ideally, you can top up the tank with premium fuel and drive it off. But if you hear a high-pitched noise or rattle, call a mechanic right away.
The engine computer will adjust the engine’s timing to minimize the impact, but there is still potential for internal damage. Best case scenario, you’ll notice reduced performance and a drop in fuel economy until the regular fuel burns out of your tank.

What happens if I mix premium and regular gas?

If you've mixed premium and regular gas, you have nothing to worry about. Premium gas has a lower octane rating than regular gas, so you'll get a mixture that's somewhere in the middle of the two.
It's not ideal and you should never mix intentionally, but you can expect your car to survive the combination. Still, be alert for any sounds coming from the engine if your vehicle is supposed to use premium fuel.
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