Diesel and gasoline engines differ in a couple of ways. First, diesel engines use a special type of fuel called diesel fuel oil. Diesel engines also don’t use spark plugs, but combust the fuel using super heated air. Like gasoline engines, diesels work on a four-stroke system, but use one of the strokes to compress and heat air inside the combustion chamber. When the diesel fuel oil is introduced to the superheated air, it combusts instantly, powering the engine. Usually diesel engines are used in large trucks, buses, and certain automobiles that don’t necessarily need quick acceleration but do require a lot of power. The diesel engine has been described as one of the most energy-efficient designs. Contact a local auto mechanic for more information on diesel engines.