The term SEMI FUEL is used to refer to two different types of fuel: DIESEL and dieseloil. DIESEL is a type of fuel made from petroleum and is composed of hydrocarbons with between 10 and 20 carbon atoms per molecule. Dieseloil, on the other hand, is a type of fuel oil derived from petroleum and is composed of hydrocarbons with more than 20 carbon atoms per molecule. Both DIESEL and dieseloil are widely used in the transportation industry, particularly in semi-trucks.