Wrong fuel in your car? Guide to removing

Last updated April 05, 2023

One distracted moment is all it takes. Accidently putting the wrong type of fuel in your car is more common than you may think; around 150,000 UK motorists make this mistake every year.

It’s something that can happen to anyone, even the most conscientious drivers. Hopefully, you will never find yourself in this situation, but it’s important to be prepared, just in case.

If you ever put the wrong type of fuel in your car, taking the correct action immediately afterwards can save your car from lasting damage – and eye-watering repair bills.

In this guide, we will cover the steps you should follow after realising you’ve added the wrong type of fuel to your car. We’ll also explain how to spot the signs that you’ve added the wrong fuel – and answer some key questions around wrong fuel recovery.

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The importance of not starting your car

If you become aware that you have added the wrong fuel before you have switched on the ignition, do not start your car. Providing you have not yet started the engine, putting the wrong fuel in your vehicle can be rectified relatively easily.

Wrong fuel in your car? Guide to removing (step-by-step)

If you’re removing the wrong fuel from your car, you should do the following:

  • Ensure the engine is switched off.
  • Explain what has happened to the petrol station staff.
  • Put your car in neutral. (Do not start the engine.)
  • Push the vehicle to a safe place.
  • Call your breakdown cover provider or a wrong fuel recovery service to drain your fuel tank.

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

The implications of adding the wrong type of fuel to your car will vary, depending on whether it is a petrol or diesel vehicle.

What happens if you put petrol in a diesel car?

Adding petrol to a diesel vehicle has more severe consequences than the reverse.

Diesel fuel acts as a lubricative oil, making sure the engine parts run smoothly and helping to minimise wear and tear. However, when petrol is added to diesel, the mixture this creates behaves like a solvent that dissolves the lubricant.

If you start your diesel car after adding petrol fuel, this mixture will circulate – and friction between the vehicle’s components will increase, which can cause damage to vital parts such as the fuel lines and pump. Petrol fuel in a diesel engine can also cause damage to the catalytic converter.

The damage caused by adding the wrong fuel to a diesel car and then starting it can be severe – and in some cases, a complete replacement of the fuel system may be necessary. If you have put the wrong fuel in your diesel car, follow the step-by-step process above to keep any damage to a minimum.

What happens if you put diesel in a petrol car?

If you put diesel fuel in your petrol car and then start your engine, the diesel will form a coating on your spark plugs and fuel system, which often leads to misfiring. You may also notice that your engine emits smoke, cuts out – or even fails to start at all.

Have you put the wrong fuel in your petrol car? Follow our step-by-step guide to avoid a crisis.

Putting E10 in an incompatible vehicle

E10 petrol became the standard grade of petrol in Great Britain in September 2021 (and in Northern Ireland in November 2022). Heralded as an eco-friendly fuel, E10 petrol is blended with up to 10% renewable ethanol and has a greener manufacturing process than many other varieties of petrol.

However, an estimated 600,000 vehicles on UK roads are not compatible with E10 fuel. So, what happens if you put E10 petrol into an incompatible vehicle?

In short, it should still run. If you mistakenly put E10 into an incompatible petrol vehicle once, there’s no cause for alarm. Just fill up with the correct fuel type as soon as possible to reduce the volume of E10 in your car’s fuel system.

However, with long-term use, metals, plastics, and seals in an incompatible car may be damaged, due to the corrosive properties of bioethanol.

What if I put E10 in a diesel car?

E10, as with any other type of petrol fuel can severely damage a diesel engine. If you realise you have added E10 to your diesel vehicle, avoid starting the engine and follow our step-by-step guide to minimise the impact on your vehicle.

How much does wrong fuel recovery cost?

A wrong fuel recovery service callout typically costs between £120-£250.

However, if you have started your vehicle after adding the wrong fuel and the engine has sustained extensive damage, the repair bill can run much higher.

A car dealership may charge you up to £800 for a fuel tank drain that does not require dismantling the tank. A major fuel system and engine rebuild may set you back between £4,000-£9,000 or more. When faced with such a steep repair bill, you may be left with no choice but to sell your damaged car and put the proceeds towards a replacement.

When using a hire car service, you should take extra care to ensure that you are using the correct fuel type for the hired vehicle. You will be subject to the terms and conditions of their contract – and may be liable to pay for the full cost of repairs if you add the wrong fuel and damage the car.

What are the signs that you have added the wrong fuel?

When you are distracted, it is entirely possible to drive away without even realising you have put the wrong fuel in your car.

However, the longer you drive with the incorrect fuel type, the greater the risk of serious damage. Therefore, it is important to be aware of the signs so that you can act decisively.

Petrol in a diesel car

If you have added petrol fuel to a diesel car, you may notice:

  • If you have added petrol fuel to a diesel car, you may notice:
  • Excess smoke coming from the exhaust.
  • Slower acceleration.
  • The engine warning light illuminating.
  • A loud knocking sound whilst accelerating.
  • The engine stopping completely.
  • Difficulties restarting your car.

Diesel in a petrol car

If you have added diesel fuel to a petrol car, you may notice:

  • Excess smoke coming from the exhaust.
  • The engine misfiring.
  • The engine cutting out.
  • The engine failing to restart.

I’ve added a small amount of the wrong fuel to my tank – will my car be fine?

It’s widely agreed that you can safely mix up to 5% petrol into diesel fuel. So, if you mistakenly add a small amount of petrol to a diesel vehicle, there’s a good chance that you can avoid any disastrous consequences.

If there is sufficient room in your tank to top it up to the required ratio of diesel, you should be able to rectify your mistake. However, if there is not, you should refer to our step-by-step guide for wrong fuel recovery.

If you add a small amount of diesel to a petrol car, it is likely that the diesel will clog up the fuel filter. Therefore, you should drain the fuel system as soon as possible.

Will I be covered by my car insurer if I add the wrong fuel?

Some car insurance providers cover damage from the wrong type of fuel in the ‘accidental damage’ section of their policy. However, you should check with your insurer to verify whether you are covered for this.

You might also be able to add ‘misfuelling insurance’ to your existing policy at extra cost for your peace of mind.

Will putting the wrong fuel in my car invalidate its warranty?

Yes, in some cases, adding the wrong type of fuel to your car can invalidate the manufacturer warranty.

For instance, if you put the wrong fuel in your car and subsequently experience engine problems, the manufacturer may refuse to pay for the repairs under warranty, if they attribute the issues to you adding the wrong type of fuel.

However, if you claim on your warranty for something unrelated to your fuelling mistake, the manufacturer may still honour your request.

For full clarity on this issue, you should refer to the terms and conditions of your vehicle’s warranty.

What happens if you mix petrol and diesel?

Just 1% petrol contamination in a diesel tank will lower the diesel’s flash point by 18 °C, meaning diesel can prematurely ignite in the engine, which can result in significant engine damage.

Petrol contamination can also cause damage to your car’s fuel pump and diesel injectors. Therefore, it is crucial that you do not start your diesel vehicle after putting the wrong fuel into the vehicle – or you could be hit with a hefty repair bill.

Other Frequently Asked Questions

You should be able to safely mix up to 5% petrol into your diesel tank without serious consequences. However, if you have exceeded this amount, you should follow our step-by-step guide to prevent lasting damage to your vehicle.

You may notice that your engine struggles or fails to start at all when you turn the key in the ignition.

However, in some circumstances the issue will only become apparent after driving away from the petrol station. Whilst driving with the wrong fuel, you may notice excess smoke, poor acceleration or other telltale signs.

As soon as you realise you have put the wrong fuel in your car, you should act quickly to prevent further damage to your vehicle.

The wrong fuel recovery process can take anywhere from a few minutes to several hours. The timescale will depend on factors such as how much of the wrong fuel type has been added - and the accessibility of the tank.

How long you can drive with mixed fuel will depend on factors such as your car’s make and model, its fuel type – and the quantity of the wrong fuel that was added. However, we would not recommend putting this to the test; the longer you drive with mixed fuel, the more likely your car will develop a serious mechanical fault.

If you are driving and have a suspicion that you have recently added the wrong type of fuel, do not leave anything to chance. Pull over when it is safe to do so. Then, contact a wrong fuel recovery specialist.

When the wrong type of fuel is added to your car, the engine will struggle to process it. Driving with the wrong fuel type will compromise engine performance and, in some cases, the engine may stop working altogether. Other important components such as the fuel system and catalytic converter may also be damaged.

Most breakdown cover policies will not cover the cost of draining your vehicle after you have added the wrong fuel. However, most will assist with moving your vehicle to a local garage, enabling you to rectify your mistake.

For a definitive answer on whether you are covered for wrong fuel repair costs, please refer to your breakdown cover policy - or contact your provider.

Whilst it is possible to drain your fuel tank yourself, we would only recommend doing so if you are familiar with the process and have the necessary tools available. Calling a professional will ensure that the tank is drained thoroughly and safely.

If you are still at the petrol station, we would recommend calling a wrong fuel recovery specialist. Do not attempt to drive home to drain your fuel tank, as this could unnecessarily damage the vehicle.