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So, what is the big deal when you accidentally put the wrong fuel in your car?

Everybody is aware that petrol and diesel fuels are two different entities. However, not all motorists are conscious how adding the wrong fuel type can cause substantial damage to your engine.This mistake is most likely to happen when you've just had a new car with a different fuel type, or maybe switching to a company car can also increase the risk. TIP: Place a large label over the fuel cap reminding you of which fuel you need to put in. Call it a bit sad, but sometimes I sing to myself in the car when going to fill up with fuel 'I'm going to the diesel station diesel station diesel diesel diesel station', as I've just switched from my petrol Renault Scenic to a Peugeot 407 estate diesel.

In fact at a garage station the nozzles on a diesel pump are generally black and larger, and are more difficult to insert into the petrol tank, particularly on the more modern cars.

Why do motors accidentally put the wrong fuel in their cars?

Over the years diesel cars have become more popular. Most people have been accustomed to driving petrol engine cars. When motorists change to diesels they forget that they had bought a car with a different fuel tank that very much requires a different fuel. Sometimes, the old memory could just lapse at that point of filling up and get distracted by day dreaming on the days events. Don't let this happen to you! Absolute concentration is required when placing your hand on the nozzle.

Additionally, over the years modern diesel cars have become much quieter which means, you don't have this lorry sounding engine to remind you it's diesel as you approach the pumps. In fact, just to throw this in there's an even bigger problem that could occur at the pumps is driving off with the nozzle still in the tank. Do you know anyone who has ever done this?

What are the consequences of adding diesel to a petrol engine?

Well, because diesel and petrol are different in the way they are refined (even though oil is the main source) then engines are built to only cope with managing the relevant fuel type. Interestingly, the most common fault is adding petrol to diesel cars as petrol used to be the most common fuel to make your journey with. The shock of then realising your driving or borrowing a diesel car then triggers the problem. Mixing the wrong fuel type is not as harsh as the other way round of adding petrol to diesel, but it can still kill your engine.

What are the consequences of adding petrol to a diesel engine?

Adding petrol to a diesel engine is particularly severe and very problematic. When petrol has been added to a diesel tank, it acts as a solvent. Furthermore, it reduces the lubrication levels and can seriously damage your engine pump system when there has been any contact with metals.

If metal is deposited in the fuel tank and beyond, there could even be further damage, not only to the fuel tank, but the injectors, pumps, fuel rails, line filters, common rails, seals and to the actual engine itself.

Adding petrol to diesel is like a virus, the deeper the contamination the harder it is for a mechanic to fix the problem. In most cases, repairing the system would be costly, it could be cheaper to buy a new engine or maybe even buy a new car.

Controversies of adding small amounts petrol to diesel

Did you know? Surprisingly, some older mechanics actually advise adding one gallon of petrol to a diesel tank, this is done approximately every four tank fill ups. Technicians suggest that this cleans out the carbon deposits out of the cylinders and is much cheaper than using a fuel injector cleaner. Have you ever heard of this been recommended?

Petrol can make diesel burn at high temperatures and nothing suggests this reduces the carbon deposits in the cylinders or helps the injectors. Higher temperatures could actually make the problems worse.

This theory originated from the older mechanics when diesel engines used to be different. There is no evidence that this actually works on modern diesel cars - what's your thoughts?

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

Try and avoid at all costs to switching your engine on. Once a motorist turns on the ignition the fuel circulates every contaminated particle around the pumps, injectors, rails, filters, seals and other parts of the engine. So, you could say the damage has been done.

Also, the longer the motorist leaves the wrong fuel type in their car the more possibilities there are your engine will have lasting problems. There are some very good companies that are willing to assist draining and replenishing your car.

Often, reliable companies can help motorists on the spot, if they can't they will inform you and advise you if it's wiser to change the engine rather than have a repair.

The RAC are specialists in draining fuel systems, they now offer a towing service if it's not possible to flush out the contamination. Members can also automatically receive a discount.

We would love to hear your views on this whole subject. Have you ever put the wrong fuel in? if so, how did you get it fixed? and at what price etc. Please let us know your experiences by entering into the comment below. We can publish them here to help other motorists in the future.