Answer from those aspects

1. Reasons for lubricant failure (1) Effect of high temperature ① When exposed to a high-temperature environment for an extended period, the lubricant oxidizes and deteriorates, becoming black and thicker. ②The amount of corrosive substances within the lubricant increases, such as acidic substances formed during engine operation. ③An increase in deposits, sludge, paint film, and other such substances. (2) Impurities mainly originate from dust in the air, metal particles, leaks (fuel, water, etc.), lubricant oxides, and substances produced by fuel combustion. (3) Failure of additives: The performance of some lubricants declines due to the failure or depletion of the additives contained in them. For example, when the anti-wear agents in lubricating oil are used up, its anti-wear properties decrease. (4) The viscosity index improver loses its effectiveness because the long chains of its organic molecules break, resulting in a loss of its viscosity-increasing property. (5) Failure of the base oil: The base oil serves as a carrier for additives; if it fails, the additives will not function.