What happens if we use petrol in diesel engine?

Most of you car or bike lovers have one doubt in mind, that what will happen if use petrol in diesel engine or vice versa?

In petrol engines, air and fuel (petrol) compresses simultaneously and then combustion takes place by spark plug.

Whereas in diesel engine, only air is compressed inside the cylinder and diesel is injected by fuel injector.

If we use petrol in diesel engine, then combustion will be abnormal. Because petrol is more volatile than diesel and it will vaporised before the compression.

This will also results in damage of piston, crank shaft, and connecting rod.

The whole phenomena is called "knocking". Here, the whole fuel system can be damaged because diesel also works as a lubricant in fuel pump and other parts.

On the hand, if we put diesel in petrol engines then simply engine will not run or start.

This is because, diesel doesn't vaporise quickly and the atomised mixture of air and diesel will not reach inside the cylinder before compression. Hence, engine will not start.


Sometimes, if the engine is too hot then because of high temperature of intake manifold and carburettor, diesel and air enters in the cylinder.

This results in damaging of entire intake system, piston, crank shaft because diesel ignites before combustion as it's auto ignition temp. is less than petrol.

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