Oxidation of a lubricant is a chemical process that changes a lubricant and makes it lose its chemical and physical properties. A quality lubricant contains antioxidant additives based on, among other things, amines and phenols. The oxidation of a lubricant starts with the breakdown of the antioxidant additives in the oil. When they are exhausted, the actual aging process of the oil starts. Some base oils, like most synthetic base oils, are naturally more resistant to oxidation. Moisture, high temperature, metal particles, UV radiation and oxides (oxygen) will accelerate the oxidation process. The consequences of oxidation are an increased oil viscosity due to the polymerization of the ox...