Type Of Base Oil and introduction

Previously, the base oil was divided into paraffin base oil, intermediate base oil and naphthenic base oil etc by major oil companies, depending on the characteristics of crude oil and production processes.

Since 1980s, the original classification of base oil was not suitable for the market trend which is focusing on the development of engine oil, then API divided the base oil into 5 groups(API-1509) in 1993. 

Group I base oil is produced by physical process like atmospheric and vacuum distillation. The structure of hydrocarbon is not changed and the quality of Group I base oil depends on the content and characteristics of ideal components of feedstock.

Group II base oil is mainly produced by chemical process like hydrogenation and solvent technologies. The structure of hydrocarbon can be changed and quality of feedstock is not important factor in the process. The characteristics of Group II base oil is less impurities(aromatic content is less than 10%) and high content of saturated hydrocarbon, good thermal stability and inoxidizability.

Group III base oil is produced by hydrogenation process and can be called hydrogenated base oil, also known as unconventional base oil(UCBO). Because of high viscosity index and low volatility, the characteristics of Group III base oil is much better.

The normal production processes of Group IV base oil are paraffin decomposition method and ethylene polymerization method. It is called poly α olefin(PAO) and can be used for modulation of different oil  products by degrees of polymerization(low, medium and high). The pour point is quite low(lower than miuns 40 ℃, viscosity index is higher than 140) because it does not contain wax. At the same time, S, P and metal are not contained in it but boundary lubricity is not good.

The other synthetic oils(synthetic hydrocarbons, esters and silicone oil etc), vegetable oil and recycled base oil etc which out of the rang of Group I~IV base oil can be called Group V base oil.