Base oil is produced by means of refining crude oil. This means that crude oil is heated in order that various distillates can be separated from one another. During the heating process, light and heavy hydrocarbons are separated – the light ones can be refined to make petrol and other fuels, while the heavier ones are suitable for bitumen and base oils.
BASE OIL CHARACTERISTICS
The characteristics of base oils determine their function and reliability. A superior mineral oil requires the best refining processes while the objective of synthetic oil is to achieve properties that are not achievable in mineral oils. Each base oil serves a different purpose, not every function can be ideally served using a single type of base oil.
Some important properties in your base oil include thermal stability, viscosity limitation, viscosity index, volatility, oxidation, pour point, hydraulic stability and aniline point (the measure of solvency with other materials and additives).
Base Oil Groups Explained
Almost every lubricant used in plants today started off as just a base oil. The American Petroleum Institute (API) has categorized base oils into five categories (API 1509, Appendix E). The first three groups are refined from petroleum crude oil.
Group IV base oils are full synthetic (polyalphaolefin) oils. Group V is for all other base oils not included in Groups I through IV. Before all the additives are added to the mixture, lubricating oils begin as one or more of these five API groups.