Both diesel engines and gasoline engines convert fuel into energy through a series of small explosions — or combustions. The major difference between diesel and gasoline is the way these explosions happen. In a gasoline engine, fuel is mixed with air, compressed by pistons and ignited by sparks from spark plugs. In a diesel engine, however, the air is compressed first, and then the fuel is injected. Because air heats up when it's compressed, the fuel igniteshttp://www.genourpowergenerator.com/engine/diesel-engine/