There are several differences between a diesel engine and a gasoline engine. First of all, a diesel engine doesn't have spark plugs. It has no carburetor. Instead, the engine takes in air and squeezes it into the cylinders until the air is very hot. The air gets so hot that when the fuel is injected into that hot air, it ignites.

What does this mean? It means that diesel engines are more efficient, meaning that it can deliver more power for the energy it uses.

On the other hand, diesel engines are not as powerful as the same size gasoline engines. An engine's power is limited by the amount of air that can be burned in the engine. In a gasoline engine there is plenty of time for the air to be mixed in during the intake and the compression stroke so the fuel can burn all the air the engine inhales.

In an ordinary diesel, only 75 percent of the air can be burned because the fuel is injected directly into the combustion chamber. That's why more and more diesels are being turbocharged.