The most important source of base oils is “crude oil”, which can be utilized in various processes to produce base oils with different specifications and applications. Crude oil does not contain a single compound and contains thousands of different hydrocarbon compounds resulting from the bonding of carbon and hydrogen elements which classified in three main groups as naphthenes, paraffins and aromatics. Accordingly, the produced base oil also includes a wide range of chemical structures among which harmful and high-risk compounds can be eliminated or transformed through the process of purification by solvent extraction, separation of low boiling point materials, the process of molecular cracking and the branching of straight-chain compounds.