What to Do If You Put The Wrong Fuel In Your Car

Filling Up Your Car Can Be Confusing.

Sometimes people accidentally use the wrong fuel, and this can lead to serious problems.

If you put the wrong fuel in your engine, it might get damaged or even stop working.

Always check what kind of fuel your car needs before filling up.

Refueling often feels simple, but it can be confusing. For instance, when using a different vehicle, you might have to call the owner to ask whether their vehicle runs on diesel or gas.

Sometimes, the problem is unavoidable, such as when the fuel’s octane is lower than what’s listed on the gas station pump.

This guide will tell you what to do if you put the wrong fuel in your vehicle.

What to Do If You Put E85 in a Gasoline Car

E85 contains more ethanol than regular gasoline. Only flex-fuel vehicles, which are specially made to handle high-ethanol fuels, can safely use E85.

• If you realize the mistake while filling up, add regular gasoline right away to help dilute the E85.
• The check engine light might turn on, but it should go off after you add regular gas to dilute the E85.
• If you only notice after you’ve started driving, just keep adding regular gas each time you fill up.

Don’t worry if you accidentally used E85. One tank usually won’t cause permanent damage, but your car might run poorly, misfire, idle roughly, hesitate, or show a check engine light.

E85 is about 85% ethanol, while regular gasoline has only 10-15%. Most cars can’t adjust their air-fuel ratio for this much ethanol. Using E85 in a regular car can eventually damage rubber seals, wear out fuel lines, and make the engine run too lean, which means it gets too much air and not enough fuel.

Over time, running an engine too lean, which means it gets too much air and not enough fuel, creates a lot of heat. This can quickly damage parts like spark plugs, exhaust valves, or even burn holes in the pistons.

What Happens If You Put Premium Gas in a Car That Takes Regular?

Using premium gas in a car designed for regular fuel won't harm it, but you'll pay more without any performance or efficiency gains.

Gas Octane Levels

Most gas stations offer regular, mid-level, and premium gasoline.

What Should I Do if I Put Premium Gas in a Vehicle That Doesn't Require It?

Using a higher-octane gas like premium in a vehicle that doesn’t require it won’t cause permanent or serious damage. However, it won’t provide any benefit either. Simply choose the recommended fuel next time to avoid unnecessary expense.

Does Premium Fuel Make Your Car Run Better?

While some people believe higher-octane fuel improves car performance, this is only true for engines specifically designed for it. In vehicles designed for regular gas, premium fuel generally won’t affect performance or efficiency, and in some cases may even lead to lower fuel economy. Stick to the manufacturer’s recommendation for best results.

What happens if I Put Regular Gas in a vehicle that requires premium gas?

If you use regular gas in a car that needs premium, the engine might knock. These engines rely on high-octane fuel to avoid early ignition. Regular gas can burn too soon, which may cause knocking, engine damage, lower performance, worse fuel efficiency, and a check engine light.

High-performance and luxury cars often require premium fuel because their engines have higher compression ratios. Using regular gas might not hurt right away, but it can lower performance, cause knocking, and wear out the engine over time.

Modern cars have knock sensors to help prevent damage, but using lower-octane fuel all the time still lowers efficiency. If your car says "premium required," stick with premium fuel.

Your car’s computer can adjust the timing if you use lower-octane fuel, but you might see worse gas mileage, slower acceleration, and hear spark knock. This knock sounds like a high-pitched ping or rattle.

• Making this mistake once probably won’t cause serious damage, but try not to do it often.
• Check your owner's manual. If it says premium is required, always use it. Don’t swap 87 for 93.
• Don’t use regular gas just to save money. It could lead to costly repairs later.

If you use lower-octane fuel in a car that needs premium, you might get worse gas mileage, lose power, and hear a high-pitched ping or rattle.

If you use lower-octane fuel for a long time, the engine’s uneven burning can cause overheating and permanent damage.

What Happens If You Put Gas in a Diesel Car?

Burning gasoline in any diesel engine will likely cause irreversible damage, and in newer, clean-diesel vehicles, even a small amount of gas will damage the vehicle’s emissions controls. By putting gas in a diesel car, you can do a lot of damage to the vehicle’s fuel injector pump. Additionally, gas combusts much more quickly in a diesel engine, which can lead to misfires and knocking, requiring repairs, rebuilds, or replacements of certain engine parts.

• If you put gas in a diesel car, stop the vehicle immediately and turn it off to avoid further damage.
• Have your vehicle towed so a mechanic can flush the gas tank and fuel lines.

What Do I Do if I Put Gasoline in a Diesel Engine?

This is the more serious of the two scenarios, as gasoline in a diesel engine can cause more permanent damage, including misfires, reduced engine power, and engine knocking.

Just as if you were to put diesel fuel in a gas engine, it is best to turn off your engine, have your car towed to our service center, and have one of our Mopar® technicians drain your engine completely. 

What Happens If You Put Diesel Fuel in a Gas Car?

What to Do if I Put Diesel Fuel in a Gasoline Engine?

Even though gas and diesel nozzles are different, mistakes can still happen. Gas engines cannot use diesel, so the engine will stop once the gasoline is gone.

If you accidentally put diesel in your gas engine, turn off the car immediately to prevent damage. Contact our service team promptly so they can drain the tank and fuel lines for you.

Although nozzle designs make mix-ups rare, act quickly if diesel is put in a gas car to avoid problems.

• The gas engine will stop when the gasoline runs out, since it cannot run on diesel.
• Take prompt action if diesel is put into a gas engine to reduce the risk of damage.
• Seek a mechanic to drain the tank and fuel lines. Arrange towing to the shop if needed.

What Happens If You Put Gas in a Diesel Car?

Running gasoline in a diesel engine can cause serious damage, especially in newer cars. Even a small amount can harm the emissions system or fuel injector pump, causing misfires, knocking, and costly repairs.

• If you accidentally put gas in a diesel car, stop driving immediately and turn off the engine to reduce damage risk.
• Have your car towed to a mechanic who will flush the gas tank and fuel lines to remove gasoline from the diesel system.

Gasoline in a diesel engine can cause lasting problems such as misfires and engine knocking.

Turn off the engine, have your car towed to a service center, and ensure the fuel tank is drained.

Putting gasoline in a diesel car is a serious mistake. Diesel engines need the lubrication diesel fuel provides, which gasoline lacks. Without this lubrication, engine parts can grind together and suffer severe damage. The fuel system must be drained, and any damage to the fuel pump and injectors repaired. In some cases, the engine may need to be rebuilt or replaced.

You can find more details above about the damage gasoline can cause in a diesel engine and what steps to take if it happens.

Gasoline and diesel engines work differently. Diesel engines use compression to ignite fuel, while gasoline engines use spark plugs. Putting gasoline in a diesel car reduces lubrication in the fuel system, can damage fuel injectors, and may cause the engine to fail completely.

Even a small amount of gasoline can harm a diesel engine. Act quickly to prevent damage.

Symptoms of Using the Wrong Fuel

Here are some common symptoms indicating you've used the wrong type of fuel:

• Engine Misfiring or Knocking: Unusual noises from the engine.
• Poor Performance: Decreased acceleration and power.
• Stalling: The engine may cut out or stall unexpectedly.
• Excessive Smoke: Unusual amounts of exhaust smoke.
• Check Engine Light: The dashboard warning light may illuminate.

What to Do If You Put the Wrong Fuel in Your Car

If you put diesel in a gas car or the other way around, turn off the engine right away. Driving any further will spread the wrong fuel through the system and make repairs more expensive. In this situation, the whole fuel system needs to be drained and flushed before you can drive safely again.

If you’ve already started driving, watch how your car acts. If you notice hesitation, stalling, rough idling, or warning lights, the wrong fuel is likely causing trouble. If everything seems normal, just fill up with the right gas at your next stop, and that should fix it.

1. If you notice the mistake before starting your car, don’t turn the engine on.
2. Call a professional mechanic or auto repair service to help and arrange for your car to be towed safely.
3. The mechanic will first drain all the wrong fuel from your tank. Then they’ll flush the entire fuel system with the correct fuel to clear out any remaining contaminants. The car should only be started again after this process is finished.
4. Have your car checked carefully for any damage to the fuel system or engine.

Repair Process

Fixing a car that’s been misfueled usually means three main steps. First, the mechanic will drain the fuel tank. Next, they’ll thoroughly flush the fuel system. Finally, they’ll replace any damaged parts, such as fuel pumps or injectors. Your mechanic should walk you through each step.