At present, base oils are divided into two main groups of mineral base oils and synthetic base oils, from the origin of the production.   

Mineral base oils 

Mineral base oils are obtained from a crude oil refining slurry. Mineral base oils are produced at three levels of quality (I, II & III) using various technologies. In this classification, by moving the base oils from the group I to group III, the viscosity index increases the saturation percentage, the percentage of base oil sulfur decreases. These properties make the lubricant, in combination with additives, more durable and more efficient.  

Synthetic oils 

Synthetic oils are produced by chemical methods. The most important synthetic base oils are poly alpha olefins, esters, and polyalkene glycols. These base oils are used to produce modern lubricants.