How many categories are there according to SAE classification?

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SAE grades represent the viscosity grades of lubricants. According to the SAE oil viscosity classification, automotive oils are specifically categorized into 4 types for summer use, 6 types for winter use, and 16 types for all-season use. Relevant details are as follows: Summer oil grades are: 20, 30, 40, 50, representing the kinematic viscosity of the oil at 100 degrees. The higher the number (the higher the viscosity), the better the protective performance of the oil at high temperatures. It should be noted that these numbers do not represent corresponding temperature values but indicate different kinematic viscosities of the oil at 100 degrees. Winter oil grades are: 0W, 5W, 10W, 15W, 20W, 25W. The symbol W stands for Winter, and the smaller the number before W, the lower the low-temperature viscosity, the better the low-temperature fluidity, and the lower the applicable minimum temperature. The corresponding oil freezing points are: 0W is -35 degrees, 5W is -30 degrees, 10W is -25 degrees, 15W is -20 degrees.