How to Identify Engine Oil Grades?

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Distinguishing engine oil grades is based on quality grades and viscosity grades. The quality grades follow the classification standards established by API, while the viscosity grades are classified according to the standards set by SAE. The classification of engine oil grades is as follows: 1. Viscosity Index: According to the SAE classification method, engine oils are divided into 6 types for winter, 5 types for summer, and 16 types that can be used in both winter and summer. Winter oil grades include OW, 5W, 10W, 15W, 20W, and 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. Summer oil grades include 20, 30, 40, 50, and 60. The larger the number, the higher the viscosity and the higher the applicable maximum temperature. All-season oil grades include 5W/20, 5W/30, 5W/40, 5W/50, 10W/20, 10W/30, 10W/40, 10W/50, 15W/30, 15W/40, 15W/50, 20W/20, 20W/30, 20W/40, and 20W/50. The smaller the number representing the winter part and the larger the number representing the summer part, the wider the applicable temperature range. 2. Quality Index: According to the API quality classification method, engine oils are divided into the gasoline engine oil series (S series) and the diesel engine oil series (C series). Each series of oils is arranged in alphabetical order (A, B, C, D, E, F) and divided into several grades. The further the letter is in the alphabet, the higher the grade.