What To Do If You Fill Up With The Wrong Fuel

It may seem like a silly mistake, but over 100,000 drivers in the UK put the wrong fuel into their cars, vans, and 4x4s every year. Filling a diesel vehicle with petrol is more common, since diesel nozzles are too large to fit into most petrol tanks, but either mixup is possible with enough determination.

Diesel is a heavier liquid than petrol, and much more "oily". Diesel requires pressure to be ignited and does not evaporate like petrol does. When you try to fire up the engine, the spark plugs won't be able to ignite the diesel and the engine won't start. Putting petrol in a diesel engine is much more complicated (and easier as mentioned above). Modern diesel engines operate at very high pressures with diesel acting as a lubricant for the engine and the injection system. However, when petrol is mixed with diesel, it acts as a thinner, causing the diesel to lose its lubrication properties and the friction will cause wear to the engine and fuel pump.

If You Are Still At The Pump

If you are still at the filling station when you realise your mistake, you can rectify the problem with minimal damage to your vehicle. It's very important at this stage that you don't start your car's engine. Simply put your car in neutral and push your vehicle out of the filling station so that it's out of the way, and inform the station attendant or call your breakdown cover organisation if you have coverage. To fix the issue, all fuel will need to be drained from your vehicle. If you have roadside assistance, this can often be done right at the station or roadside. If you don't have roadside coverage, your car will need to be taken to a garage - but do not attempt to fire the engine up. Once all fuel has been drained, the tank will need to be filled with the appropriate fuel and primed to remove any air leaks from the fuel system. To be extra safe there is no remaining wrong fuel in the system, change the fuel filter.

If You Have Started To Drive

If you began to drive and your car only to find it suddenly came to a halt, it's a much bigger problem. Once you have turned your vehicle on, the incorrect fuel will make its way to your engine and cause major damage. Petrol is much more volatile than diesel, plus diesel relies on high pressure to combust. With the high pressure and air, if petrol enters a diesel engine, the petrol will prematurely combust and force pistons out of their order. At this point your only real solution is to call your breakdown company. They will have to tow cars, vans or 4x4s in this situation to a garage to inspect the damage. The bill to repair such damage can often be in the four-figure range. On older vehicles you may want to check with your insurance company, as it may be easier to simply write the vehicle off rather than undertake costly repairs.

How To Avoid Putting The Wrong Fuel In Your Car

Of course, the obvious solution to avoiding such issues is to be attentive when filling your vehicle. If you are letting a friend or family member borrow your vehicle, make sure to tell them what type of fuel your vehicle uses. You can make it extra clear by placing a sticker on your fuel cap labelled with the appropriate fuel type, which will act as a reminder to anyone when they go to fill up the tank. If your vehicle is not already fitted with one, it's also possible to purchase fuel neck caps for diesel vehicles that will prevent putting petrol into a diesel tank by not allowing the nozzle to fit.


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