Car insurance can be a minefield, and new research has shown that nine out of ten insurers won't pay out to drain a car after misfuelling - the easy mistake of putting petrol in a diesel engine or vice versa.

Drivers are being urged to check their policy as the cost to fix a misfuelled car can range from £120 to more than £10,000, plus the price of the wasted fuel. 

Every year, there are about 150,000 incidents of misfuelling in the UK, with the majority of cases involving putting petrol into a diesel car.

More drivers are now at risk of getting caught out by expensive misfuelling costs due to changes in insurance products, says Defaqto, which put together the report. 

Only around one in ten (11 per cent) of products now provide a drainage service benefit, where cover is provided towards the costs of draining the incorrect fuel from the car. 

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Mike Powell, Motor Insurance Expert at Defaqto, says: "It is easy to put the wrong fuel in a car, but it can cause terrible damage to the engine, and in the worst cases, result in complete engine failure. 

"Repairing this type of damage can run to thousands of pounds, making it a costly mishap for unlucky motorists. Cover may be provided under the accidental damage section of a policy, but fewer providers are now giving accidental damage cover following a misfuelling incident."

If you do misfuel, some products will provide cover for someone coming out to recover your car to a garage so that the fuel can be removed. However, this only includes the cost of the recovery, not any additional costs for the removal of the incorrect fuel.

But, the Defaqto data shows that nearly a third (32 per cent) of motor breakdown products exclude recovery from misfuelling incidents altogether.  

The most important thing to do when you have misfuelled is to not start the engine. If you realise you put the wrong fuel into your vehicle before you turn the ignition on, things are much easier and less expensive to fix. 

"However, if you turn on the engine, the wrong fuel is pumped through your vehicle and you may be forced to replace the fuel pump, pipes, injectors or even the entire engine," says Mike. "A high performance engine could result in a bill of £10,000 or more."

Here are Mike’s top tips on what to do if you put the wrong fuel in your car: 

  1. Don’t start your car and if possible push it to somewhere safe.  
  2. If you’ve already driven away, don’t panic. Find a safe place to pull over as soon as possible and turn off the ignition immediately.
  3. Check your car insurance policy documents to see if misfuelling is covered. If it is, call your car insurance provider for assistance.  
  4. If you have breakdown cover, call for assistance. Your cover may include the cost of towing, draining and cleaning.
  5. If you don’t have breakdown cover, you can call a breakdown company to help out. However, they might need you to become a member or charge you an additional fee for the call-out.