ABSTRACT
Formulated lubricating oils are designed to meet many requirements and one of the most important ones is that the operating life of the oil be as long as possible. This is achieved if the lubricants maintain their “as new” properties (i.e., the physical and chemical properties of the lubricant change as slowly as possible during use). The principal factor affecting the life of a lubricant is oxidation of the base stock, which is the major component of the oil. Some additives in a finished lubricant are there specifically to protect the base stock from oxidation. Oxidation causes the formation of volatile oxidation products, corrosive acids, sludges, lacquer deposits, surface active compounds, and high molecular weight oxidation products. These can cause a decrease in flash point, an increase in viscosity, poorer oil-water separation, less corrosion protection, deposit formation, and increased wear.
