Why Can’t I Put Diesel in a Petrol Engine?

It’s pretty common knowledge that filling up your car with the wrong fuel is a recipe for disaster. The incorrect fuel in a car can be very damaging if you try to run the engine, so it’s vital to have the fuel drained as soon as possible should the unthinkable happen.

However, have you ever wondered exactly why this is bad for an engine? What happens if you put diesel in a petrol car? Well, read on and we’ll explain!

Diesel in a Petrol Engine

Unlike petrol, diesel fuel is oily and doesn’t evaporate quickly. It’s also heavier than petrol. This is because diesel contains longer hydrocarbon chains than petrol, ultimately meaning that it is a lot less volatile. It’s harder to ignite than petrol, so there is a difference between petrol and diesel engines. Knowing how each engine works will help you to understand why misfuelling is so harmful to car engines.

The air in a diesel engine is compressed, causing it to become superheated; the fuel is then injected, igniting it in the hot air. In a petrol engine, the fuel mixes with air and is ignited by spark plugs.

So, in a situation where diesel is put into a petrol car, the fuel would be injected, causing the spark plugs to fire, but the fuel would not ignite and engine would never start. This is the situation if it is entirely diesel fuel in the engine.

If it’s a mixture of petrol and diesel in the engine, which is usually the case when a misfuelling occurs, then the car would run extremely inefficiently and produce a lot of thick smoke. Attempting to run a petrol engine with a significant amount of diesel fuel in the tank is not an advisable plan if you want your engine to remain in good condition.

Conversely, petrol that finds its way into a diesel engine will burn up almost immediately due to the volatile nature of petrol and the mechanics of a diesel engine. This will cause the engine to splutter, running extremely inefficiently and it’s quite likely to cause some quite serious and expensive damage.

So, if you find yourself in a situation where you’ve put the wrong type of fuel in your car (it happens to the best of us!), then do not hesitate to give WrongFuel a call on 0800 634 9827.