Petroleum products such as gasoline, kerosene (jet-fuel), diesel fuel, lubricants, paraffin wax and bitumen are manufactured from crude oil using a range of refining processes including distillation, cracking, isomerisation, reforming, alkylation and hydrodesulphurisation.

However, refineries use a variety of process plants operating under different conditions. The chemical composition of crude oil feedstocks also varies widely, so the type and quantities of different hydrocarbons present in output streams from the same manufacturing processes can vary both within and between refineries.

Further support can be found through the Environmental Science for European Refining Industry (CONCAWE).