A diesel engine is an engine that uses diesel fuel to run. Diesel fuel is made from crude oil and it is a type of fuel that is different from gasoline. Diesel engines are more powerful and efficient than gasoline engines. They use a different type of combustion cycle from gasoline engines. In the combustion cycle, air is pushed into the cylinders of the engine, and diesel fuel is injected. The fuel and air mix together and then explode, which causes the engine to move and turn. This process helps the engine to be more efficient and powerful than a gasoline engine.