What does SAE mean for engine oil?

[McEmerson]

Engine oil SAE grade represents the viscosity level of the oil. SAE classifies engine oils by viscosity into: 1. Winter oil grades: 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. 2. Summer oil grades: 20, 30, 40, 50. The larger the number, the higher the viscosity and the higher the applicable maximum temperature. 3. All-season oil grades: 5W/20, 5W/30, 5W/40, 5W/50, 10W/20, 10W/30, etc. The smaller the number before W, the better the fluidity of the lubricant at low temperatures, making it easier to start the car. The larger the number after W, the better the viscosity of the oil in high-temperature environments, forming a stronger oil film. It belongs to the all-weather type.