These oils are used as the base for the preparation of a huge array of products. The best known of them are the lubricants.Base oils are rated according to their chemical constitution as paraffinic and naphthenic
The American Petroleum Institute classified it in 5 types of lubricant base oil:
Group I Base Oil – Which Saturates less than 90% and/or sulphur> 0.03%, and viscosity index (VI) of 80 to 120 These are manufactured by solvent extraction, solvent or catalytic dewaxing, and hydro-finishing processes. Common Group I base oil is 150SN (solvent neutral), 500SN, and 150BS (bright stock)
Group II Base Oil – Which Saturates greater than 90% and sulphur< 0.03%, and SAE viscosity index of 80 to 120 & manufactured by hydrocracking and solvent or catalytic waxing process. Group II base oil has superior anti-oxidation properties since all hydrocarbon molecules are saturated. Colour of this Group base oil is water-white.
Group III Base Oil – Which Saturates at greater than 90%, sulphurless than 0.03%, and SAE viscosity index over 120 Manufactured by special processes such as ISO hydromerization. These can be manufactured from base oil.
Group IV Base Oil – Polyalphaolefins
Group V Base Oil –naphthenic, PAG, esters and not included in above Groups.