Diesel fuel is very similar to heating oil, which is used in central heating. It is produced from various sources, the most common being petroleum. Other sources include biomass, animal fats, biogas, natural gas, and coal. Now, diesel fuel is often referred to as ULSD (ultra low sulfur diesel). ULSD is cleaner and contains a maximum sulfur content of 15 ppm.
Diesel fuel is widely used in most types of transportation. The gasoline powered automobile is the major exception. Unlike gasoline engines, diesel engines do not use spark plugs. An engine running on diesel compresses the air inside the cylinder to high pressures and temperatures causing the fuel to react with the oxygen in the mix, heating and expanding the burning mixture which moves the piston. Diesel engines burn the fuel in more air than is required for the chemical reaction and thus use less fuel than a regular engine.