People make mistakes when dealing with a car. Sometimes it is the owner’s mistake and sometimes it is somebody else’s. Putting diesel in a petrol car could be counted as a big mistake. In this article, we will try to explore what happens when you if diesel does enter a petrol car and what are the possible solutions.

Basic differences between petrol & diesel engines

diesel in petrol car

Petrol engines and diesel engines have a different way of operating. Petrol engines use spark plugs to ignite the fuel that in turn creates a blast in the engine that pushes the piston, ultimately leading to the production of power. The diesel engine, on the other hand, uses compression pressure to increase the temperature of diesel fuel, which on reaching a specific temperature, auto-ignites and the production of power happens. Now, both fuels also have different physical properties. Petrol is a thin fuel, whereas diesel is thicker.

What happens when diesel enters a petrol engine?

diesel in petrol car

As mentioned above, diesel is a thick fuel. When it enters the fuel line & fuel filter, it gets clogged due to its dense nature, which the fuel system of a petrol engine is not meant to deal with. Further, if somehow any fuel does manage to move further, it will clog the fuel injectors as well. With no fuel reaching the main chamber, the engine would misfire due to the almost zero ignition and the car would stall.


The solutions depend on how quickly you respond to the situation and how far has the damage been done. In case you instantly realize the mistake, the fuel can be swapped. This would in a way dilute the diesel with petrol, making it convenient for the diesel to mix with petrol and burn. However, if it has not come to your attention and you believe that a major chunk of your fuel tank is filled with diesel, the best thing to do is to not turn on the ignition. With the ignition turned on, the fuel would start circulating in the system, which would make problems worse. Also, the problem needs to be quickly dealt with. The car should be towed to a garage and the fuel should be drained out. The fuel tank should be filled with petrol and again drained in order to remove any diesel residue. This repetition of this process would depend on the diesel residue remaining. Also, the fuel filter should be cleaned as soon as possible. However, if the car has stalled, this would require a thorough cleaning of the system.

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