GB/T 14906-1994 "Viscosity Classification of Internal Combustion Engine Oil" stipulates the viscosity classification system of internal combustion engine oil. The standard divides internal combustion engine oil into multiple viscosity grades based on the viscosity characteristics at different temperatures, and defines the viscosity range and performance requirements corresponding to each grade. Through this standard, it provides a unified basis for the production, selection and mass evaluation of internal combustion engine oil, which helps to ensure the lubrication effect and normal operation of the engine under different working conditions.