The Science Behind Misfuelling

Fuel is a commodity that we use every day, sometimes without even thinking about or knowing it. If you drove to work today, or got the bus, then the vehicle that you travelled in will use either diesel or petrol to get you to your destination.

Fuel is used to drive the engine of any vehicle, but surely every fuel is the same, right? I’m afraid not! We will be looking into the different types of fuel and what happens if you put the wrong one in your car.

Petrol Pump

Diesel and Petrol

Both of these fuels come from a common primary source; crude oil. This is extracted from oil fields, such as the one in the North Sea. Petrol and diesel are derived from a component of crude oil that is distilled known as petroleum. Once petroleum is distilled, it is split into different components that are used for various scenarios.

One component is called gasoline, which people normally refer to as petrol. Another component is called diesel oil, which people simply refer to as diesel.

Putting Diesel in a Petrol Engine

This is one of two possible scenarios when it comes to misfuelling your vehicle. In a petrol vehicle, the engine works via an ignition process; the spark plugs within the engine ignite the petrol which then causes the pistons to oscillate and thus, make the car move.

If you put diesel in a petrol engine, you will firstly notice some resistance when you put the nozzle into the vehicle. The reason this occurs is because diesel fuel nozzles are larger than petrol fuel nozzles, meaning that is reasonably difficult to fill your petrol car with diesel.

However, if you do not notice, the diesel will not be able to ignite, as a lot of pressure is required to activate the diesel. Since diesel is heavier than petrol, it will not ignite and simply clog the fuel injectors. This then means that the spark plugs will not be able to function properly, leading to the engine not being able to turn on at all.

Luckily, fixing the issue is relatively easy. Essentially, the tank needs to be drained and then refilled with petrol, the fuel injectors need to be thoroughly cleaned, and then cleaning the rest of the engine intake. Once this has been completed, the engine should start up again with no issues whatsoever.

Hood of old diesel tractor

Putting Petrol in a Diesel Engine

This is the second scenario of misfuelling your vehicle. In a diesel vehicle, the engine works via a compression process; there are no spark plugs present, since diesel engines have a larger compression ratio, meaning that the fuel mixture inside the engine can ignite by itself.

If you put petrol in your diesel engine, then the situation is much more serious. Firstly, it is a lot easier to put a petrol fuel nozzle in a diesel engine compared to the other way round, so a first glimpse you won’t know if you’ve used the wrong fuel nozzle.

Another issue is that, since diesel is denser than petrol, diesel acts as a lubricant within the engine, enabling the engine to function correctly without any issues. However, since petrol is less dense than diesel, it means that, in a diesel engine, petrol acts as a thinner, meaning that the engine and the fuel injectors can wear down due to friction.

Another issue is that, due to the high pressures in a diesel engine, it could result in petrol igniting quicker than it should, since it is more volatile than diesel, and can cause a reasonable amount of damage to the engine block. To fix this, a repair of the engine needs to be undertaken, so be careful with what you put in your engine.

Engine technology

When filling up your car, always double check what you are putting in. Also, if you have realised that you put the wrong fuel into your vehicle, don’t turn the engine on, as this would cause more damage. At Wrong Fuel, we specialise in taking care of your car if you have put the wrong fuel in. If you want to know more about the services we can provide, then please don’t hesitate to contact us.

Simply call us today on 0800 634 9827 and one of our incredibly friendly members of staff will be more than happy to help.