The production method varies by base stock group. Additional complexity exists for base stocks produced from used oil. The first step in the production of “virgin” base stocks, those produced from crude oil, is distillation. Distillation is used to separate molecules based on boiling point into streams suitable for upgrading to fuels, and those which can be upgraded to lubricant base stocks. After distillation, various steps involving separation and/or molecular transformation are used in the production of base stocks.

Group I base stocks are conceptually the simplest to manufacture and are produced by separating molecules by solvent-assisted processes. The two primary processes involved in the manufacture of Group I base stocks are solvent extraction, which removes polar molecules thus improving the oxidative and thermal stability of the base stock, and solvent dewaxing, which removes wax and improves the low temperature fluidity of the base stock.

Group II and Group III base stocks are generally produced from distilled crude oil streams upgraded through high pressure catalytic processes involving hydrogen. The first step in the process involves hydrotreating and frequently hydrocracking. Hydrotreating saturates aromatic species in the feed stream and removes virtually all sulfur and nitrogen from the feed. Hydrocracking involves further conversion of hydrocarbons in the feed primarily to boost the viscosity index of the resultant base stock. Dewaxing and hydrofinishing via catalytic processes follows with the goal of converting wax species, preferably by isomerization, to reduce the pour point of the base stock, improve its low temperature fluidity, and to improve its oxidative stability. Group III base stocks differ from Group II in that they generally originate from high quality feeds and may require more severe processing.

Some Group III base stocks are produced by natural gas or coal conversion to synthesis gas, carbon monoxide and hydrogen, which is converted by the Fischer-Tropsch process and subsequently upgraded in a way similar to convention Group III base stocks.

Unlike most other base stock suppliers, ExxonMobil manufactures base stocks globally. ExxonMobil has invested heavily in expansion and improvement projects in Rotterdam, the Netherlands, Baytown, Texas, and Jurong, Singapore (ongoing), which allow truly global production of high-quality base oils with a reliable supply.

Since base oils are most often made from crude oil, an increase in the price of oil will cause a base oil price increase. This can mean base oil prices vary between base oil suppliers. Reach out to one of the sales representatives in your region to learn more about base oil prices.