RAC Cars News


Have you put the wrong fuel in your car?

By raccars Published

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Some people say that it's an easy mistake to make while others will point and laugh at your misfortune but statistics show that filling up with the wrong fuel is a common error. Unfortunately using the wrong fuel can, in some cases, cause catastrophic damage to your engine and cost you a great deal of money.

Petrol is the wrong fuel in a diesel car!

Manufacturers have sensibly taken steps to guide you towards using the right fuel, which includes coloured rings around the filler neck and using a larger nozzle on diesel pumps to make sure that they won't fit into the filler neck of a petrol car. However, by definition, the nozzles on petrol pumps will still fit into the filler neck on a diesel car and this is how 95 per cent of mis-fuelling errors occur.

If you realise that you've made a mistake within a matter of moments, some mechanics will say that it's safe to remove the petrol nozzle and carry on with diesel, provided that the final mis-fuelling ratio is not more than 1/20. If there's a chance that your diesel fuel tank will contain more than five per cent petrol once full then don't risk it. You will need to contact a professional mechanic to arrange to have your fuel tank emptied and then flushed clean. This usually costs about £200 and takes 30-40 minutes.

Do not turn the key

You should be able to avoid any serious damage provided that you haven't switched on the ignition. However, you will almost certainly be facing some inconvenience, expense and probably some humiliation. Even before you've turned your key all the way, if your dashboard lights have illuminated then your fuel pump may have kicked in, which means the wrong fuel is already starting to circulate through the car's engine. At this point not only will you have to drain and flush the fuel tank but also the fuel lines which are now carrying petrol to your diesel engine.

If you switch on your ignition however the real problems start. Diesel passing through the fuel pump provides lubrication. Petrol is a solvent and will remove that lubrication, without which the mechanical parts of your fuel pump will create friction and grind together. This process releases tiny metal particles which travel further into your car's engine.

Next in line is the high pressure injector array, which pushes fuel through tiny holes in a specific pattern. These holes will quickly become blocked by these floating particles of microscopic metal which have been ground out of your fuel pump. A new injection system can cost thousands. Furthermore, petrol can corrode seals in a diesel engine.

Once petrol has entered a diesel engine, the whole system will need to be examined in detail for damage and flushed with a cleaning solution.

Take quick, decisive action

The sooner you realise and take steps to rectify your mistake, the more likely you are to escape serious damage. Some motorists can even get a few miles down the road before the car conks out, and yet may in some cases escape with their engine unscathed. Unfortunately the likelihood is that driving even a small distance will cause damage and will certainly cost you money to repair. The more assessment and cleaning a mechanic has to do, the more your mistake will cost.

The best thing to do is swallow your embarrassment and ask for help as soon as possible. If you haven't yet started the car, don't. Enlist the help of fuel station attendants to push it out of the way then call your breakdown recovery operator or a mis-fuelling recovery specialist if you don't have breakdown cover.

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