Diesel oil is a mixture of light petroleum products, complex hydrocarbons (carbon atom number about 10 ~ 22), for diesel fuel, mainly from crude oil distillation, catalytic cracking, thermal cracking, hydrocracking, petroleum coking and other processes to prepare diesel distillate, can also be produced by shale oil processing and coal liquefaction. It is divided into two categories: light diesel (boiling point range of about 180 ~ 370℃) and heavy diesel (boiling point range of about 350 ~ 410℃).

The most important use of diesel is for diesel engines in vehicles and ships. Compared with gasoline engine, diesel engine has high thermal efficiency and low fuel consumption. Diesel has low energy consumption, so some small cars and even high-performance cars have switched to diesel.