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Misfuelling cover

What do you do when you put the wrong fuel in your car?

Putting the wrong type of fuel in your car is surprisingly common – and you can cover yourself against it

By Mehdi Punjwani

Published: 18 August 2021

Refuelling a car

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What is misfuelling?

Misfuelling is the simple mistake of putting the wrong type of fuel in your car at the petrol station. It’s much more serious if you put petrol into a diesel car than vice versa, but you should follow the steps below in any event.

It is very bad for the engine if you turn it on before you realise – but there are solutions if you catch it in time.

Misfuelling is a surprisingly common problem. The RAC estimates that around 150,000 UK drivers put the wrong type of fuel in their car every year, so you’re in good company!

What should I do if I put the wrong fuel in my car?

If you’ve noticed you’ve filled your car with the wrong fuel at the pumps, do not turn on the ignition. This causes the most serious damage from misfuelling.

If you’ve already driven away from the petrol station, find a safe place to pull over as soon as possible and then turn the engine off.

After the car is off, follow these steps:

  1. Take the key out of the ignition
  2. If you’re still at the petrol station, inform the staff
  3. Put the car into neutral and move it somewhere safe
  4. Check your insurance documents to see if you have breakdown cover or misfuelling cover
  5. If you are covered, call your insurer
  6. Call a breakdown service – if you’re not a member you will probably need to pay for the call-out

What happens when you put petrol into a diesel car?

Putting petrol into a diesel car is a much more serious problem than putting diesel into a petrol car – but the damage can be limited by making sure the engine is switched off and the keys are out of the ignition. These are the signs:

  • There’s a banging sound when you accelerate
  • Your exhaust gives off too much smoke
  • Acceleration is slower than normal
  • Your engine light goes on
  • The engine cuts out

Diesel cars use their fuel as a lubricant, helping prevent wear and tear on the moving parts. Adding petrol to the mix dissolves the lubricant, and when you turn on the ignition this solvent causes a lot of friction in the engine.

It will quickly damage the system – especially the fuel lines and pump. Worse still, repairs are normally expensive and you may even be forced to replace the whole fuel system.

What happens when you put diesel into a petrol car?

Accidentally putting diesel in a petrol car is less severe, but you should still turn the engine off as soon as you can and get it sorted.

The diesel infiltrates the spark plugs and fuel system, which causes the engine to smoke and cut out. It may not even start at all.

What is E10 fuel?

E10 fuel or E10 petrol is a new standard grade of petrol to be rolled out in Great Britain in September 2021. In Northern Ireland this should happen in early 2022.

What is the difference between E10 and E5 petrol? 

E10 petrol contains up to 10% ethanol, a renewable fuel that will help petrol vehicles lower their carbon dioxide emissions. E5, the fuel has been used up until this change, is only up to 5% ethanol.

Will E10 fuel work in my car? 

Any cars newly manufactured since 2011 are required to be compatible with E10 petrol, while many cars and motorcycles that were manufactured in the late 1990s and later are also likely to be compatible. 

The government estimates that 95% of petrol powered vehicles will be able to run on E10 petrol*. However this won’t always be the case – you may find the following vehicles are not compatible:

If your vehicle isn’t, then you’ll still be able to use E5 – you will just need to purchase ‘super’ grade petrol. 

The government have a useful tool that lets you check if your vehicle can use E10 fuel.

*Figure from government website

What happens if I misfuel my car with E10 petrol? 

If you put E10 fuel in an incompatible car, it may cause damage over an extended period of time – even if it still runs in the short term.


Does car insurance cover misfuelling?

A few car insurance policies include misfuelling as standard, but many insurers will ask you to pay a monthly small surcharge for cover as an optional extra.

Some insurers do not offer misfuelling cover at all.

A decent misfuelling insurance policy should pay for the following:

  • Draining and cleaning the fuel tank, either at the petrol station or at a service centre
  • Reimbursing some or all of the cost of the contaminated fuel

However, some policies won’t pay out if you’ve driven further than a specified distance while using the wrong fuel.

Compare misfuelling cover

The best way to get a good deal on misfuelling cover is to compare car insurance using MoneySuperMarket.

We compare policies from dozens of insurance companies; all you have to do is give us some information on you, your circumstances and your car, and we’ll do the rest. If you want misfuelling cover, make sure to specify that on the form.

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