Gear oil is divided into two categories: automotive gear oil and industrial gear oil, each of which follows different standards, so they cannot be mixed and substituted. Internationally, automotive gear oils use SAE viscosity classification standards. In recent years, due to the mass production and sales of imported brand gear oils in China, automotive gear oils in the domestic market basically use SAE viscosity classification labels.

SAE is the abbreviation of Society of Automotive Engineers. SAE has established viscosity standards for automotive gear oil and automotive engine lubricating oil (motor oil).

Significance of SAE viscosity classification: Viscosity is the most important performance index of lubricating oil. The greater the viscosity, the better. Selecting a lubricating oil with a suitable viscosity according to the car manual is the first step in lubricating oil selection. Gear oil is a part of lubricating oil. Therefore, when choosing, the viscosity is the first step. According to the SAE classification standard, all automotive gear oils can be divided into two categories: single-grade gear oil and multi-grade gear oil (or double-grade gear oil, double-grade gear oil).

Different types of gear oils, even with the same viscosity, cannot be substituted at will. Different lubricating oils contain different base oils and additives to meet the needs of different working conditions of the equipment. For example, ordinary industrial closed gearboxes usually use mineral oil to meet the requirements, while for wind turbine gearboxes, it is necessary to use anti-oxidation Synthetic oil with good performance; as another example, for medium-load gearboxes, L-CKC grade gear oil can meet the requirements, but for heavy-duty gearboxes, L-CKD heavy-duty gear oil with better extreme pressure performance must be used .

Under normal circumstances, the replacement of oil products follows the principles of "substituting good for poor" and "substituting high for low". Use higher quality grades instead of lower quality grades (such as L-CKD heavy-duty gear oil instead of L-CKC medium-duty gear oil), but whether it is "replacing poor with good" or "replacing low with high", when replacing Beforehand, it is best to entrust a professional testing agency to conduct an alternative evaluation analysis to reduce the risk of oil replacement.