Diesel engine is a type of internal-combustion engine used chiefly for heavy-duty work. Diesel engines drive huge freight trucks, large buses, tractors, and heavy road-building equipment. They are also used to power submarines and ships, and the generators of electric-power stations in small cities. Some motor cars are powered by diesel engines.
Diesel engines have a high thermal efficiency, or ability to convert the stored chemical energy in the fuel into mechanical energy, or work. They burn a fuel that is cheaper than petrol, and they can perform heavy work under highly overloaded conditions. This is why they are favoured for heavy-duty work.
