What to do if you put the wrong fuel in your car? (Q&A)

Lisa Harper

By: Lisa Harper

Accidentally putting the wrong fuel in your car is a relatively common problem and something that many of us have either done or know someone who has done it. Whether you’ve just switched cars and you’ve automatically filled up with the fuel your old car took or you’ve got a million things on your mind and have just not been concentrating when at the fuel station, it’s easy to do.

WhatCar claim someone in the UK puts the wrong fuel in their car approximately every three and half minutes. Whilst the RAC state over 150,000 people every year fuel up with the wrong fuel. So if you do put the wrong fuel in your car you’re certainly not alone!

What happens if you put petrol in a diesel engine?

Diesel acts as a lubricant within the engine and helps to reduce friction and wear between vital engine parts. When petrol is mixed with diesel it creates a solvent which has the opposite effect and causes more friction between engine parts so it can quickly cause damage. The more petrol that pumps through the diesel system the worse the damage will be. Just starting a diesel car that has been incorrectly fuelled could result in expensive repairs being required.

What happens if you put diesel in a petrol engine?

Putting diesel into a petrol engine is less detrimental and less easy to do. Diesel nozzles are usually larger than petrol nozzles so actually fitting a diesel nozzle into a petrol car can be difficult.

Unlike petrol, diesel needs to be compressed in order to ignite. The lack of compression means that diesel fuel within a petrol engine is unable to ignite and therefore the engine is unlikely to start at all. However diesel fuel within a petrol engine can cause the spark plugs and the fuel system to clog up.

putting the wrong fuel in your car

What should you do if you put the wrong fuel in your car?

DO NOT START THE ENGINE!

- If you’re lucky enough to realise your error before starting the engine do not start it. Let an assistant at the fuel station know that you’ve put the wrong fuel in your car.

- You’ll then need to move your car out of the way whilst you wait for help. Put the car in neutral and get help pushing it out of the way.

- If you have breakdown cover give them a call and they should be able to come out to you and perform a fuel drain and flush. You’ll also need to inform your insurance company.

- If you don’t have breakdown cover and aren’t covered for misfuelling on your insurance the fuel station may be able to give you the number for a local company offering fuel drain and flush services.

What happens if you drive off after putting the wrong fuel into your car?

If you drive off after putting the wrong fuel in your car the chances are you won’t get far. Your car is likely to make some grumbling noises so take heed and pull over as soon as you can. If you still don’t realise your car will eventually grind to a halt, but at this point it is likely there will be considerable damage.

What are the consequences of putting the wrong fuel in your car?

The AA state that the average price for misfuelling is around £190 which includes the cost of call out, fuel drain, flush and replenish of your fuel system.

However putting the wrong fuel in your car can cause substantial damage to your engine and result in your car being off the road for some time whilst it has costly repairs. The RAC suggest that as a worst case scenario it could cost in the region of five thousand pounds!

damage caused when you put the wrong fuel in your car

Will your insurance cover you if you put the wrong fuel in your car?

Some insurers won’t cover misfuelling, whilst others cover it under accidental damage. Some insurers will cover the entire service whilst others will only cover the damage and won’t cover any breakdown costs. We recommend checking with your insurer to see where you stand.

How can you prevent putting the wrong fuel in your car?

- Make sure you’re concentrating when you go to fuel up

- Don’t just rely on the colour of the pump to indicate the fuel, read the text on the pump as well

- If in doubt which fuel is which don’t be afraid to ask a fuel station assistant for help

- Fit a diesel fuel cap to your fuel neck which prevents a petrol nozzle fitting in, prices for a diesel fuel cap range from around £15 to £30

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