FAQs

Flush Fuel – Frequently Asked Questions

If you cannot see the answer to your particular question here, please feel free to call and ask us. A member of our team will be more than happy to help.

Help! I’ve put petrol in a diesel car. What do I do now?

First of all, do not turn on the ignition or start the car. Running the engine with even a small amount of petrol in a diesel car might damage the engine and fuel system which may invalidate any warranty you may have on your vehicle. Call Flush Fuel immediately on 07546 799181 and one of our engineers will come out to you, to assist. In most cases, a small amount of petrol in your diesel car should not damage the engine as long as you have not started the car and our engineer completely drains or flushes all of the petrol from the fuel tank and tops it up fully with diesel fuel.

If you’ve added more than 10% (5 litres in a 50 litre tank) petrol we will need to drain the fuel tank of all the petrol and then refill with diesel fuel. If you’ve added less than 10% petrol (5 litres in a 50 litre tank) – we may be able to fill up the tank with diesel fuel and run the car normally unless the manufacturer advises otherwise.

Help! I’ve put diesel in a petrol car. What do I do now?

Whatever you do, do not turn on the ignition or start the car. It is much less common to put the wrong fuel in a petrol car than to put the wrong fuel in a diesel car because the standard diesel nozzle at fuel stations is larger than the fuel filler neck on modern petrol cars – the simple fact that the filler neck won’t accommodate the diesel nozzle means you have to be pretty determined and patient to misfuel your petrol car with diesel. If this should happen, call Flush Fuel straight away and we will be there to assist as quickly as possible.

Generally, a small amount of wrong fuel in your car should not damage the engine, as long as you have not turned on the ignition or started it and you then make sure you top up fully with petrol.

If you’ve added more than 10% (5 litres in a 50 litre tank) diesel – we will need to fully drain the diesel fuel from the tank and refill with the car with petrol. If you’ve added less than 10% (5 litres in a 50 litre tank) diesel – we may not need to drain or flush the diesel fuel from the car and may be able to fill the fuel tank with petrol unless your manufacturers warranty (should you have one) says otherwise.

I’ve put the wrong fuel in my diesel car what is the potential damage?

Diesel engines have fuel pumps that work on very fine tolerances and are lubricated by the actual diesel fuel itself. Petrol in diesel fuel acts as a solvent – it reduces the active lubrication and causes damage to the pump through the sheer metal to metal contact.

Some advanced fuel system seals can be affected by the compounds in petrol too. As a rule of thumb the further the contaminated petrol goes in the system the more expensive the repair costs will be. Some manufacturers advise that seals and filters should be renewed even if the engine has not been run. This particular remedial action will not be nearly as expensive as having to replace the entire engine.

The newer HDi diesel engines, or common rail systems, are particularly vulnerable – if the fuel that has been contaminated by pump wear creates debris and this gets as far as the common rail system you may also have to replace the low and high-pressure fuel pumps, injectors, fuel rail, line filters and the fuel tank too. This shows what a nightmare can be created by the simple act of putting the wrong fuel in your car.

Many diesel engines use a low-pressure electric pump in the tank or sender unit and this begins to work as soon as the ignition is switched on, circulating the contaminated fuel through the pump and rail – so if you’ve put the wrong fuel in your car it’s important not even to turn the ignition on and the engine must certainly not be started.

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