What to do if you’ve put the wrong fuel in your vehicle

5 steps...

author image-grace
By Grace Hickman
Updated on Friday 10 September 2021

Driver putting petrol into his car

Accidentally putting petrol into a diesel car is easily done by drivers as the petrol nozzle can fit with ease into a lot of diesel filter necks, making it a common mistake.

Putting diesel into a petrol car, however, is less common because the diesel pump nozzle is usually larger than the majority of petrol filter necks, making it more difficult to fill a petrol car with diesel. For this reason, it isn’t as common - but it can still happen.

Read below to find out exactly what you should do in the event of misfuelling.

Have you put the wrong fuel in your car? - Here’s what to do and what NOT to do

Firstly, if you’ve put the wrong type of fuel in your vehicle, you MUST NOT start the car and attempt to drive it.

If you are a member of a breakdown company, such as the AA, you may have a type of cover known as ‘fuel assist’ as part of your policy (you may even have this protection with your car insurance policy), in which case, you will need to call them immediately for professional assistance. 

Here are 5 steps to follow if you’ve misfuelled your car:

  1. Do not turn on the ignition: If you try to start your vehicle with the wrong type of fuel in it, this will cause severe and permanent damage, leaving you facing very expensive repairs. If the keys are in the ignition, just remove them completely.
  2. Let the staff in the petrol station know what’s happened so they are aware of the situation.
  3. Make sure the car is in neutral and move it to a safe place: If possible, try to get someone nearby to help you push the car to a safe location so as not to be in the way of other drivers. And of course, ensure that the car is in neutral with the handbrake down and NOT turned on when doing this - once it’s in a safe spot, put the handbrake back up to make sure the car is securely parked.
  4. Call a misfuelling expert who can help:  You’ll need to contact someone professional who can help drain and flush your fuel system. This could be your breakdown provider, insurer or local specialist (found while searching for a wrong fuel specialist on Google near you). If you’re really not sure what to do, chances are, the staff in the petrol station will know what you should do and who you should call.
  5. Call your car insurance provider: Your insurer (or breakdown cover provider) might be able to offer cover that can pay for the cost of having your fuel tank drained or your engine repaired (if necessary).

What happens if you accidentally put the wrong type of fuel in your car?

If you’ve put diesel in your petrol car or vice versa and you try to start it (because you haven’t realised what you’ve done), you’ll experience the following:

  • The engine won’t start
  • The engine will start but it’ll soon cut out and stop working
  • The exhaust system will start producing a lot of smoke

If any of the above happens, take the key out of the ignition immediately to avoid further costly damage and seek help.

Putting petrol in a diesel car

If you accidentally put petrol into a diesel tank, this actually causes more damage to your vehicle than if you were to put diesel into a petrol car.

Petrol fuel can damage your diesel car in the following ways:

  • It causes increased friction between the different parts of the diesel engine, whereas diesel helps the fuel pump work as it should, acting like a type of lubricant.
  • The friction caused from this will cause more problems.
  • The more petrol that gets pumped through the diesel engine, the more problems and damage will be caused to your vehicle.

For the reasons mentioned above, this is why it’s crucial that you do not try to start your car after misfuelling, to avoid the wrong fuel being pumped through the engine.

If you do start the car and allow the wrong fuel to be pumped through, this could lead to you having to pay for new:

  • Fuel pumps
  • Injectors
  • Pipes
  • Filters
  • Fuel tank
  • Engine (worst case scenario)

Putting diesel in a petrol car

As we mentioned above, this situation is not as bad as putting petrol in a diesel vehicle. Also, it’s more difficult to make this mistake as the diesel pump probably won’t be able to fit into the petrol filter neck, making it a much less common occurrence.

However, if you do manage to accidentally put diesel into your petrol car, the diesel will clog up the spark plugs and fuel system, so the vehicle will not start at all.

After the diesel has been drained out of your petrol car, you shouldn’t be left with any severe, permanent damage.

Putting AdBlue in your fuel tank by mistake

Accidentally putting AdBlue into your fuel tank is also another common problem for cars that use AdBlue.

As with putting petrol in your diesel car and vice versa, do not attempt to start the car if you have mistakenly put AdBlue into the fuel tank - otherwise, you’re likely to face a huge repair bill.

You must call a professional out to help you - AdBlue is corrosive, so it cannot be drained at the petrol station or roadside, meaning that the person or company you call will need to tow your vehicle to the nearest garage to get the problem fixed.

Alternatively, you may have accidentally put petrol into your AdBlue tank - again, do not try to turn on the engine and make sure you call a professional straight away. They will probably have to replace the whole AdBlue system, which will come with a price of course.

How much does it cost to drain and flush the fuel system?

There is no fixed price for rectifying a misfuelling accident, as the cost will largely depend on the type of car and engine you have, as well as whether you have started the car with the wrong fuel in or not.

The AA states that the general cost for calling out a fuel recovery specialist is £190 (or around £274.99 with the RAC if it needs to be towed to a garage to be fixed - members get a £50 discount) - provided you have not tried to start the engine after misfuelling.

If, however, you have started the engine with the wrong fuel, the cost is likely to be a lot higher. The RAC states that costs could go as high as £5,000 depending on the severity of damage.

How many people put the wrong fuel in their car every year?

If you’ve put the incorrect fuel into your vehicle, don’t worry, you’re not the only one who’s make this mistake.

According to the RAC, as many as 150,000 motorists in the UK put the wrong fuel into their vehicle every year, so it’s a lot more common than you may think and there are plenty of professionals around to solve the problem.

The most important thing to remember is to not turn on the car if you put the wrong fuel in.

Things to remember to avoid making a misfuelling mistake again

If you’ve misfuelled your car and been through the hassle of getting it fixed, you’re going to want to avoid doing this again at all costs, and there are a few ways in which you can prevent misfuelling in the future.

  • You can put a sticker or label on the petrol cap so that you (or someone else who drives your car) knows exactly what type of fuel to put in.
  • Check the colour of the petrol pump and ensure you read the labels as colours are not the same with all petrol stations.
  • Make sure you have full attention when putting fuel in your car - get rid of any distractions or avoid getting fuel if you are stressed or in a rush, as there’s a higher chance of making a mistake.
  • If your vehicle has a diesel engine, you can buy a type of stopper that goes into the diesel filter neck - this will make sure that if you ever go to accidentally use the petrol pump, the petrol nozzle will definitely not fit through the diesel filter.
  • Sometimes, the petrol and diesel hoses get tangles up together, so always check to see whether or not they’re tangled and if they are, take the time to untangle them and ensure you’re using the correct pump.

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