What to do if you misfuel

If you’ve accidentally put the wrong fuel in your car, don’t turn on the ignition or start the engine. This will circulate the contaminated fuel and increase the risk of expensive damage.

What to do if you misfuel

‘Misfuelling’ seems to be associated particularly with the growth in diesel car sales. Modern diesels are so quiet it’s easy to forget you’re driving one, particularly if it’s a second family car or hire car.

Potential Damage

Diesel fuel pumps operate on very fine tolerances and at very high pressures – modern systems run at between 350 and 1600 bar – and are lubricated by the fuel. Petrol in diesel acts as a solvent, reducing lubrication, and can cause damage to the pump through metal to metal contact.

The further the contaminated fuel goes in the system the more expensive the repair. In some cases, it can be cheaper to fit a new engine!

Petrol in Diesel

* Don’t turn on the ignition or start the car *

In line with car manufacturers’ recommendations, AA advice is that any diesel fuel contaminated with petrol should be removed from the tank and replaced with clean fuel before the ignition is turned on and the car started.

Diesel in Petrol

* Don’t turn on the ignition or start the car *

This is less common because the standard diesel nozzle is bigger than the filler neck on modern petrol cars.

In line with car manufacturers’ recommendations, AA advice is that any petrol contaminated with diesel should be removed from the tank and replaced with clean fuel before the ignition is turned on and the car started.

Reduce the Risk

No one misfuels deliberately and no one expects it to happen to them, but hundreds of motorists put the wrong fuel in their vehicle every year.

  • you use an unfamiliar filling station – don’t assume hose colours are the same as your ‘local’ site
  • you switch between brands using different hose/nozzle colours
  • you swap cars (using different fuel) at home or work – it’s easy to ‘forget’ which car you’re filling
  • you hire a car using different fuel to your normal car
  • you buy a new car using different fuel to your old car
  • you continue a conversation with passengers while filling up
  • you are in a hurry/running late

Alex Todd Brand Manager at BoxyMo commented "The simplest way to avoid it is to always ensure you are aware of the type of fuel your car needs. This is important if other people drive the car, or if you’re using a hire car."


Full story can be read via theaa.ie

About BoxyMo


BoxyMo.ie is Ireland's first telematics dedicated insurer. This new concept is simple, we fit a telematics device, known as “BoxyMo” to your car. BoxyMo will then tell us how you drive and how far you drive. In addition to this “BoxyMo” will show you each month how to improve your driving and reduce your insurance costs. read more...


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Boxymo.ie is the trading name for MCL Insurance Services Ltd. MCL Insurance Services Ltd who is authorised and regulated by the Financial Conduct Authority of the United Kingdom, and is regulated by the Central Bank of Ireland for conduct of business rules. MCL Insurance Services Ltd, Registered in Northern Ireland, Company number NI41174. Registered Office, 66 Railway Road, Coleraine, Co Derry, BT52 1PG.