Misfuelling is more common than you might think, and this guide covers what to do if it happens and whether your insurer will cover the cost.
Key takeaways
- Around 150,000 UK drivers put the wrong fuel in their car each year. It's an easy mistake to make.
- If you're still at the petrol station, don't start the engine. This helps prevent serious damage.
- Putting petrol in a diesel car is usually more damaging than putting diesel in a petrol car.
- Breakdown cover can take your car to a garage, but it usually won't pay for the repairs. Your car insurance may cover this, depending on your policy.
- Repairs usually cost £120-£1,000, but they can be much more expensive if you've started or driven the car.
What is misfuelling?
Misfuelling means putting the wrong fuel in your vehicle. It's an easy mistake to make - around 150,000 drivers do it yearly.
Most often, drivers put petrol into a diesel car. That's because petrol nozzles are smaller and fit easily into diesel tanks. Diesel nozzles are larger, so they usually don't fit into petrol tanks. This makes putting diesel in a petrol car much less common.
Is misfuelling covered by car insurance?
It depends on your car insurance policy, not all include misfuelling cover as standard.
Some insurers cover the full repair cost as standard. Others might only cover parts, like draining and cleaning the engine. Check your policy details to understand your cover, or call your insurer.
What damage can misfuelling do to my car?
Misfuelling can seriously damage your car. Whether it's petrol vs diesel or diesel vs petrol, the type of damage depends on which way round you've mixed them up. Here's what happens.
What happens if you put petrol in a diesel car?
Putting petrol in a diesel car can cause major damage, even total engine failure. Diesel engines need the lubrication from diesel fuel to keep parts running smoothly. Petrol strips this lubrication away. Without it, your car's metal parts rub together, causing friction and wear that leads to problems like:
- Damaged fuel injectors. These spray fuel into the engine. If they break, your car might struggle to start, run roughly, or stop completely.
- Pump failure. The fuel pump moves fuel through the engine. Diesel lubricates it, but petrol makes it wear out or break. This stops fuel from flowing properly.
- Engine breakdown. Without the right fuel and lubrication, engine parts grind together. This can lead to expensive repairs or even a full engine replacement.
What happens if you put diesel in a petrol car?
Good news: putting diesel in a petrol car usually causes less damage than the other way around. But it can still lead to costly repairs.
Petrol engines need spark plugs to ignite fuel. Diesel is thicker and less flammable, so it won't ignite properly.
This often stops the engine from starting. Usually, draining the tank and refilling with petrol solves the problem. But if the engine does start with diesel in it, you might notice:
- Difficulty starting. Petrol engines need spark plugs to ignite fuel, but diesel won't burn properly. Your engine might not start at all.
- Engine problems if it starts. If your car does run, you might see it smoking, stalling, or cutting out suddenly. The engine could also run very roughly, causing more damage.
What should I do if I put the wrong fuel in my car?
Misfuelling is a common, stressful mistake.
Here's what to do, depending on when you realise:
- Still at the pump? Don't start the engine. If you haven't started your car, don't. Starting it could seriously damage the engine.
- Already driving? Pull over safely and switch off. If you've started driving, pull over as soon as it's safe. Turn off the engine and put the car in neutral.
- Tell the petrol station staff. Let them know what's happened. They can help you move your car to a safe spot away from the pumps.
- Call your breakdown company. They can drain the tank and get you to a garage. Remember, breakdown cover usually won't cover the repair bill itself - your car insurance policy often handles this.
- Contact your insurer. Tell your insurer what's happened. If misfuelling is covered by your policy, they'll give you the next steps.
"Breakdown cover will usually get you off the forecourt and to a garage, but it won't cover the repair bill. That's down to your car insurance, and only if it includes misfuelling cover. Always check both policies rather than assuming you're fully covered." What our motor insurance expert says
What happens if I misfuel with E10 fuel?
If you accidentally put E10 petrol in a vehicle that isn't compatible, don't stress! You usually don't need to drain the tank. Just fill it up with the correct fuel as soon as you can to dilute any E10 left inside. This simple step prevents issues.
But regularly using E10 in a car that isn't compatible could lead to internal damage over time. E10 contains 10% renewable ethanol, compared to premium unleaded, which contains 5%. While most modern cars are designed to handle it, some older vehicles might not be.
Check if your car is E10 compatible on GOV.UK.
How do I make a claim for misfuelling?
Here's how to claim:
- Check your policy first. Find your insurer's contact number and confirm you're covered for misfuelling. This saves time later.
- Call your insurer ASAP. The sooner you get in touch, the quicker they can assist you.
- Gather receipts. Keep any receipts for repairs or breakdown services. Your insurer will ask for these as proof.
Will I lose my no claims bonus?
It's possible, but not guaranteed.
A misfuelling claim might reduce your no claims bonus, but it rarely wipes it out completely. The impact depends on your insurer's rules and the claim's severity.
Check your policy documents to see exactly where you stand.
Will my insurance go up?
Your premium could go up.
Insurers often adjust your premium after a claim, even for something minor like misfuelling.
Before you claim, work out the repair cost plus your voluntary excess. This helps you decide if claiming is worth it or if paying for it yourself makes more sense.
How much will the repair be?
This depends on the damage. Putting diesel in a petrol car usually causes more issues, leading to higher repair bills. On average, repairs cost £120 to £1,000, according to Which.
Top tip: Find local garages and get a few quotes from them before you go ahead.
How can I prevent misfuelling?
Avoid a costly mix-up at the pump with these simple tips:
- Always double-check the fuel type before you start filling up.
- If you drive a diesel car, use a stopper. It stops the smaller petrol nozzle from fitting into the tank.
- Add a sticker to your fuel cap that clearly states whether your car is diesel or petrol.
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