Diesel Engine vs Gasoline Engine (What’s the Difference?)

(Updated on April 17, 2020)

Diesel engines and gasoline (petrol) engines are two internal combustion engines that are most commonly found in automobiles. They both have similarities and differences between them.


One big similarity is they are both 4 stroke engines. The 4 strokes of these engines include intake, compression, combustion, and exhaust. When it goes through the intake stroke it pulls fresh air into the cylinder.

This is where the compression stroke generates hot gas by compressing the air in the cylinder. At this point, the fuel is ready to be burnt inside the hot gas. Then the combustion stroke generates power from this once the piston absorbs the fuel’s energy.

Then finally, the exhaust stroke releases the carbon emissions from the burnt gas into the atmosphere. Diesel engines and gasoline engines go through this same process.


So what are the differences between the two engines? Well, the main difference is how the fuel actually burns. The fuel used in gasoline engines evaporates very easily into the air after it gets released. But what’s really fascinating is that it only takes a spark for the combustion stroke of a gasoline engine to absorb energy from the fuel.

The minimum temperature required for this combustion is called the flash point. The flash point of a gasoline engine is -45°F, whereas the flash point of a diesel engine is 126°F.

As you can see, the diesel engine is not as volatile during its combustion stroke because diesel fuel does not mix well with air. This means that diesel fuel should only be mixed with air during the combustion stroke phase with the use of a fuel injector.

Gasoline engines, on the other hand, can have its fuel pre-mixed with air because of its volatility. Rather than using a fuel injector, gasoline engines only need spark plugs.

Diesel engines may be heavier and louder than gasoline engines, but they are generally more fuel efficient because the diesel engines are only compressing air. But the power produced by diesel engines is so intense and unbalanced that they are more commonly used in heavier vehicles like trucks and buses. Gasoline engines are better for lighter vehicles like 4-wheel cars and 2-wheel motorcycles.

Just be careful not to mix the wrong fuel with a particular engine. Diesel fuel inside a gasoline engine will simply fail to cause any combustion.

However, if you place the highly volatile gasoline into a diesel engine then it would enter into the chamber that has highly compressed air and then cause a detonation instead of combustion. This would ultimately destroy the engine and force you to get a new one.

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