GB/T 12709-1991 "Determination of aging characteristics of lubricating oils (Conn's residual carbon method) " standard specifies a specific method for determining the aging characteristics of petroleum-based lubricating oils. This method is suitable for petroleum-based lubricating oils with evaporation loss not exceeding 15% (m/m), including lubricating oils with or without additives, and lubricating oils containing antioxidant additives and ash cleaning dispersants. During the test, the sample is passed into the air twice at 200 ° C for 6 hours each time to simulate the aging process. The aging characteristics of lubricating oils are evaluated by measuring the residual carbon value of the samples before and after aging. This standard provides a reliable way to assess changes in lubricants Stability and performance in high temperature environments.