What Happens If You Put the Wrong Gas in Your Car? - Fuel Express (2023)

Nov 9, 2015 | General Information

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What Happens If You Put the Wrong Gas in Your Car? - Fuel Express (1)

On a daily basis, most of us drive a car or truck that requires regular, unleaded gasoline. This makes it pretty simple when we fill up at the gas station. But every once in awhile, someonemayaccidentally fill their vehicle with a different gasoline than usual.

What should you do if this happens?

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Most of today’s vehiclesare technologically advanced enough to tell the difference between lower octane gas and higher octane gas (regular and premium); cars and trucks haveelectronic fuel management systems that will notice the switch and adjust the ignition timing and fuel injection to cope.

If you usually fill your tank up with 87-octane gasoline and you accidentally put in a higher octane blend (say, 91, 92, or 93), don’t worry. You’re actually fillingyour car or truck with a differentblend of gas, which means it will burn differently in your engine. You may feel a difference in the way the vehicle runs and may notice an improvement in gas mileage, but that’s about all that will happen.

Premium Gas Vehicles

If your car or truck manufacturer recommends premium gasoline for your car and you put in regular,don’t panic. Just because premium is recommended doesn’t mean you have to use it; you can easily use regular gas without compromising the engine.

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However, if your manufacturerrequirespremium gasoline and you put in regular, you may have some problems. Depending on how advanced your vehicle’s fuel system is and other factors like how your engine is tuned, what the timing is, and how hot it runs determines how your car or truck will handle regular gas. In most cases, the vehicle will run fine, but you may experience less power and a decrease in gas mileage. In more serious cases, you may hearengine knocking or valve chatter because the fuel isn’t burning right. These things could damage your engine and you should take it to your mechanic.

Diesel Vehicles

Diesel fuel is very different than unleaded fuel, and it’s important that you pay attention to which your vehicle requires.

If your vehicle requires diesel fuel and you accidentally put in unleaded, the unleaded fuel will actually remove the lubrication that diesel provides for the car’s parts. That means the parts will grate against each other and cause big damage.

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If the opposite happens and you fill your regular gas-car with diesel, the damage may not be as bad, but you’ll only get a few miles down the road before the engine cough, sputters, and loses power. You’ll need to flush out your fuel lines and refill the car or truck with diesel, but you’ll be able to drive it again.

If you’ve filled your car with the wrong type of gasand haven’t turned it on yet, do yourself a favor and don’t. Once the wrong fuel is drawn up into the fuel lines, you’ll experience engine damage.Instead, call a mechanic and have them rectify the situation.


What happens if I accidentally put the wrong gas in my car? ›

You'll most likely notice the spark knock (a sort of high-pitched pinging or rattling noise). Luckily, the engine computers can adjust the timing to limit the amount of damage caused, but you'll definitely notice lower fuel economy and reduced performance in your vehicle.

What happens if you accidentally pump 87 instead of 91? ›

If the octane rating is less than 91, you could damage the engine and may void your vehicle warranty. If heavy knocking is heard when using gasoline rated at 91 octane or higher, the engine needs service.”

What happens if you put regular gas in a car that only takes premium? ›

However, remember this: when a premium fuel engine runs on regular fuel, there's a risk of combustion of the fuel mix before the spark plug even lights up. This causes a phenomenon called knocking, which is likely to damage the engine. Although Mazda recommends using premium fuel, they don't require it.

Can mixing different gas damage your car? ›

"In most cases, the vehicle will run fine, but you may experience less power and a decrease in gas mileage. In more serious cases, you may hear engine knocking or valve chatter because the fuel isn't burning right.

Can you mess up your car if you put too much gas? ›

But in essence, topping off your gas tank can cause pressure to build in the tank and flood the carbon filter vapor collection system, only meant for vapor. As a result, the overflow can affect your car's performance and could possibly damage the engine.

What will happens if you mix unleaded and premium gas? ›

Can I mix premium and unleaded gas? Yes, drivers can mix the two types of fuel. The combined gas types will result in an octane level somewhere in the middle — something the vehicle “will survive,” according to The Drive.

What happens if you don't run premium gas instead of regular? ›

Using a Lower Octane Than Required

Filling your premium only vehicle with regular gas can actually trigger engine knocking so significant that parts of your engine could suffer damage. In many cases, such damage is often not even covered by manufacturer warranties.

What happens if I put 89 instead of 87? ›

If you use a lower-than-recommended octane, fuel can combust too quickly for your engine to take full advantage of it. This combustion causes knocking, which sounds like a light pinging or rattling noise. It's a result of the air-fuel mixture in the cylinders igniting too early.

How do you remove gas from a car? ›

Get under the car and find the drainage plug.

Make sure your pan is directly under the plug. This plug is simply a small bolt screwed directly into the tank. Opening it simply creates a hole for gas to drain out. You usually need a spanner or socket wrench to remove it.

Do all gas pumps shut off automatically? ›

Gas pumps are mechanically designed to automatically stop pumping gas as soon as the tank is full. The nozzle valve shuts automatically once the gasoline blocks the air in the Venturi tube.


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