What Happens If You Put the Wrong Gas in Your Car?

It doesn’t happen quite often, but imagine a scenario where you drive into a pump station only for you to pump the wrong gas in your car. What happens? Will your car even be able to run, or will it cause damage to your engine?

In most cases, nothing severe will occur. However, it pays to take action immediately!

That’s why in this article, we will guide you on understanding what happens if you put the wrong gas in your car and the necessary steps to take in solving the problem and preventing extreme damage to your vehicle. 

What Happens If You Put Diesel in a Gasoline Car?

Putting diesel in a petrol engine is not likely to happen, primarily because the diesel nozzle is a bit large, making it hard to fit in a petrol tank mouthing. However, it does still happen occasionally…

Diesel and petrol primarily differ in terms of composition. Therefore, you can expect something terrible to happen if you mistakenly fill a gasoline tank with diesel fuel.

Gasoline engines cannot operate with diesel because, naturally, diesel doesn’t combust easily. On the other hand, car engines running on petrol cannot burn such fuel.

Once you fill the tank with diesel, your vehicle won’t ignite.

Once you realize the mistake, the first thing you should do is turn off the engine immediately to prevent any potential damage to your car engine. Next, waste no time draining all the diesel in the tank and fuel lines to protect the engine’s internal components.

It’s possible to do this by yourself, but the Automobile Association recommends seeking the services of an automotive professional who will also inspect for any damages. 

If you run the engine with even the smallest amount of diesel in your petrol tank, you’re potentially damaging it. Your vehicle will smoke heavily, and you won’t like how rough the engine will run.

What Happens If You Put Gasoline in a Diesel Car?

Filling up a diesel tank with petrol is the most dangerous fueling mistake. That’s where the differences between the two gases become more evident!

Once you fill a diesel engine with gasoline, it causes significant damage almost instantly to the fuel pump and fuel injector.

Remember, gasoline and diesel are very different.

For one, gasoline is lighter and flashes at a lower temperature than diesel. Gasoline in a diesel engine has the following adverse effects:

Petrol is lighter and ignites at a lower temperature. Therefore, it will flash fast, causing knocking and misfiring, and probably damage your engine permanently. The shockwaves due to detonation may destroy the engine’s pistons, connecting rod, and wrist pins.

In addition, diesel acts as both a fuel and lubricant. So, adding gasoline will damage the engine and may even result in inadequate lubrication of the engine components, causing damage once they rub against each other. 

You should note that too much gasoline in a diesel engine is detrimental. If you try to start the car, it may result in the engine failing or getting damaged beyond repair. 

What should you do once the mistake happens? Immediately you realize the unexpected has happened, turn off the car at once. Then, have your vehicle towed to an automotive shop where a professional mechanic will drain all the gasoline from the diesel tank and fuel lines.

Note that trying to do the draining yourself is risky because if you do it incorrectly, it may result in damages that ultimately cost you more than it would to tow your car to an auto repair shop for professional assistance.

Gasoline and diesel pump nozzles

What Happens If You Put High Octane Fuel in a Regular Gas Car?

Regular gas has an octane rating of around 87, while premium gas is a high-octane gas with a rating of 91 and 93.

So what happens if you fill up your regular gas car with premium gas?

Putting premium gas in a regular gas tank is a most common mistake as the fuel nozzles are basically identical. Aside from potentially having a different colored nozzle coating, there’s no other obvious difference!

Additionally, a good number of motorists can’t differentiate the octane levels. Also, some believe using a higher-octane fuel boosts the performance of your car. But does your car need the higher-octane gas?

In most cases, filling up your regular gas tank with higher octane fuel will have no added benefit, nor will it have any effects on your car engine. That said, there are some cars where the performance gets better.

But there’s no need to worry if you find that you’ve made such a mistake. No significant damage will happen to your engine, and you don’t need to trouble yourself draining out the gas.

Just drive to the next nearest station and fill your tank with the proper fuel, and any problems experienced will vanish.

What Happens If You Put Low Octane Fuel in a Premium Gas Car?

I have on several occasions heard people driving cars operating on high-octane premium gasoline saying how they fill up with cheap fuel to save on costs. That’s not advisable

Filling up a car designed to operate on premium gas with a low-octane fuel is detrimental. You’ll feel the effects almost immediately!

Some of the consequences include:

  • The car will knock before you even leave the pump station.
  • There will be a significant reduction in your car engine’s performance, and you may even destroy your motor.
  • If you continue using the low-octane fuel for long, you’ll be altering the fuel detonation. This can result in inconsistent combustion, damaging your car engine’s internal components. In addition, your engine will become susceptible to frequent overheating.

Fortunately, most modern cars will have their ECU (Engine Control Unit) adjust the engine timing and performance, and the car will run well with low-octane fuel. If you fill up with regular gas, make sure to switch to premium fuel as soon as you can refuel your vehicle. 

You can also learn more about this in my dedicated article on switching from premium to regular gas.

How Can You Prevent Misfuelling?

Well, humans are to err, and from time to time, you may find yourself filling up with the wrong fuel. While I haven’t done it myself, I know that some of my friends have made this mistake in the past…

Nevertheless, here are some ways you can minimize such occurrences:

  • Always look for other clues rather than rely on the color of the nozzle when refueling.
  • Before filling up, read the trigger label on the pump correctly and the fuel grade indicator to ensure you are pumping the suitable gas.
  • If you just bought a new car which consumes a different gas from your previous one, I recommend you put a reminder. For example, you can place a sticker with the fuel type on the inner side of the fuel tank cap. 
  • When you get to a pump station, focus on filling up and avoid distractions. For instance, keep your phone away for the few minutes you attend to your fuel tank.
  • Try always to fill up when you’re not in a hurry, stressed, or hungry, as mistakes are likely to happen during such times.
  • If you own a diesel car, look for a device, such as a stopper that fits into the filler neck so that the narrower petrol nozzle won’t fit in. 

Final Word

Filling up your vehicle with the wrong gas is a common mistake. Should you experience that, you won’t be the first to experience this. The most important thing is to understand your next course of action to prevent damages to your engine. 

If you take the measures mentioned above, you can be sure no severe or permanent damage will happen to your car engine. Otherwise, as mundane as it may be, always pay attention when filling up your car to avoid mis-fuelling.

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Hi, I'm the founder of VehicleAnswers.com! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!