Misfuelling
What to do if you've put the wrong fuel in your car
You're not alone. It's estimated that at least 150,000 drivers put the wrong fuel in their car each year – one every three and a half minutes!
And the scale of the problem has been getting bigger too, especially over the last five years with growth in diesel car sales – modern diesels are so quiet it's easy to forget you're driving one, particularly if it's a second family car or hire car.
If you've put the wrong fuel in your car, don't turn on the ignition or start the engine as this will circulate the contaminated fuel and increase the risk of damage.
Potential damage
Diesel fuel pumps operate on very fine tolerances and are lubricated by the diesel fuel itself.
Petrol in diesel acts as a solvent – it reduces lubrication and can cause damage to the pump through metal to metal contact.
Some fuel system seals can be affected by the compounds in petrol too.
The further the contaminated petrol goes in the system the more expensive the repair – it can be cheaper in more extreme cases to fit a new engine.
The newer common rail (or HDi) diesel engines are particularly vulnerable – if fuel contaminated by pump wear debris gets as far as the common rail system you may have to replace the low and high-pressure fuel pumps, injectors, fuel rail, line filters and the fuel tank too.
Many systems 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 it's important not to turn the ignition on.
Petrol in Diesel
If the car's still under warranty you should check with the franchised dealer regarding the correct remedial action – some manufacturers advise that seals and filters should be renewed even if the engine has not been run.
- Modern diesel with common rail or unit injectors – if you've added any petrol at all then the car shouldn't be started and the tank must be drained.
- Other diesel engines (not common rail or unit injectors)
- More than 10% (5 litres in a 50 litre tank) petrol – Drain the tank and refill with diesel
- Less than 10% petrol – Top up with diesel and run normally
Diesel in Petrol
This is much less common because the standard diesel nozzle at fuel stations is larger than the fuel filler neck on modern petrol cars – you have to be pretty determined and patient to misfuel with diesel as a result.
- Petrol car with a catalytic convertor
- more than 4% (2 litres in a 50 litre tank) diesel – the car shouldn't be run and the tank should be drained
- less than 4% diesel – the tank can be topped up with petrol and the car run normally
- Older car without a catalytic convertor
- avoid running the car and get the tank drained if you've added more than 10% (5 litres in a 50 litre tank) diesel.
AA Fuel Assist
In November 2007 the AA launched Fuel Assist, a specialist roadside service that drains, flushes and replenishes vehicle fuel systems on the spot, saving the customer both time, money and inconvenience.
AA Fuel Assist is available to the general public as well as to AA Members and will attend any vehicle providing the Fuel Assist van has enough capacity in its tanks.
The service not only retrieves the contaminated fuel but ensures that it is recycled through a waste management company with the end product being used to power cement kilns and furnaces for example.
- Price starts at £176.25 (£150 plus VAT) for AA members and £199.75 (£170 plus VAT) for non-members
- Fresh fuel to refill the tank is charged at pump price
- Operates Monday to Friday, 8am till 8pm
- An appointment system is in place
- Bookings and enquiries number for AA Fuel Assist is 0870 240 3985 (opening hours 7.30am till 7pm)
- Dedicated, trained technicians – who only do fuel drains, not general breakdowns – arrive within an hour, on average
- Fuel AssistSM is a registered Service Mark
More information about AA Fuel Assist.