What to do if you put the wrong fuel in your car

Last updated by mustard.co.uk on June 29th, 2017

Whether you’ve put diesel in your petrol car or petrol in your diesel car, putting the wrong type of fuel in your vehicle can be a costly mistake.

Fortunately, most new cars have a system to prevent misfueling but that doesn’t stop it happening, with 150,000 motorists putting the wrong fuel in their car every year.

What should you do if you put the wrong fuel in your car?

It doesn’t matter if its petrol in diesel or vice versa, there are a couple of things you should do immediately when you misfuel:

1. Don’t start your car

Starting the car will mix both types of fuel and begin to circulate the fuel around your engine. This will damage your engine.

2. Push your car to a safe place

Get help to push your car in neutral to a safe location.

3. Contact a mechanic or garage

If you’ve misfuled your best bet is to contact a mechanic or garage to explain the problem.

In most cases if you haven’t started your car and driven with two fuels inside your engine, draining the fuel should be enough to solve the problem.

I’ve put petrol in a diesel car

Putting petrol in a diesel car is worse for your engine than putting diesel in a petrol car.

That’s because diesel cars use the fuel as a lubricant. As petrol is corrosive, it can damage the inside of your engine as it’s not built to withstand petrol.

On top of that, petrol will reduce the lubrication of your car’s fuel pump, meaning different components will rub together, causing damage and the formation of metal particles in your fuel.

Once the fuel begins to pump through the engine, these particles spread, causing damage further down your fuel system and the further down the damage, the more expensive the repairs.

Symptoms of petrol in a diesel car

– Your vehicle struggles to start
– Your exhaust emits smoke when driving
– Your engine is noisy
– Your car loses power at high speed after 20 minutes of driving
– Your engine won’t stop once it’s running

How to fix your car if you’ve put petrol in a diesel engine

What needs to be done to fix your problem really depends on the amount of petrol you’ve pumped into your diesel car and whether you’ve turned on the ignition.

More often than not the solution will be a full drain, removing all contaminated fuel from your car and cleaning any other sections of your fuel system that have been affected.

If you’ve driven with contaminated fuel, it will be an expensive fix.

In some cases, if you’ve only put a small amount of petrol into your diesel car (usually less than 10 per cent of your fuel tank’s full capacity) filling up with diesel should be enough to solve the problem.

It’s best to leave it to the experts if you’re unsure.

Help! I’ve put diesel in a petrol car

If you had to pick a way to misfuel, putting diesel into a petrol car is the one to choose because it’s much less serious.

Usually, the worst thing that will happen is a misfiring engine – but it’s usually solved by a full fuel tank drain.

Symptoms of diesel in a petrol car

– Your engine misfires
– Your engine won’t start
– Your engine cuts out
– Your exhaust emits smoke when you’re driving

How to fix your car if you’ve put diesel in a petrol engine

Usually there’s little serious damage if you put diesel in a petrol car and it’s just a case of getting rid of the contaminated fuel and carrying on as normal. It’s sometimes advisable to flush your fuel lines with clean petrol as well.

If you’ve put a small amount of diesel in your petrol car (five per cent of your fuel tank’s capacity or less), filling your car up with clean petrol should be enough to solve the issue, however most garages and mechanics will recommend a full drain too.

The only real issues come about if you’ve driven your petrol car with contaminated fuel. In cases like this you may need to change your fuel filter.

It’s worth knowing that not all insurance policies cover misfuelling and if it does there may be restrictions. Some policies may cover the cost of repair others may only cover the cost of draining and cleaning, so make sure you check your policy details to know exactly what your covered for.

If your policy doesn’t include misfuelling cover you can still buy it as an optional extra.

Comparing quotes online at mustard.co.uk gives you the best opportunity to see a range of policies meaning you can make an informed decision about what’s available and for how much. Or, if you’d prefer to get a quote over the phone please call 0330 022 8387 and one of the team will be happy to help.

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