Does engine oil have a shelf life?
1 Answers
Engine oil does have a shelf life. The shelf life of engine oil (fully synthetic, semi-synthetic, and mineral oil) is generally 4 to 5 years. The contamination and deterioration of stored engine oil are mainly caused by its exposure to moisture, oxygen, and impurities in the air. Therefore, opened engine oil must be sealed for storage. Under normal circumstances, the water content in engine oil is below 0.03%. When the water content exceeds 0.1%, the additives in the engine oil (such as antioxidants, detergents, dispersants, etc.) will become ineffective, accelerating the oxidation process of the oil. The organic acids generated by the oxidation of engine oil and the acidic oxides in the engine exhaust gases react with water to form inorganic acids. These acidic substances increase the corrosion of the engine. When the engine oil contains a significant amount of water, its lubricating properties deteriorate, and the viscosity decreases. In mild cases, this leads to premature oil deterioration and rusting of engine parts; in severe cases, it can cause serious engine failures such as bearing seizure and connecting rod bearing damage.