What does the engine oil model number mean?

[AlexLee]

In the SAE engine oil viscosity specifications: 1. "W" stands for Winter, and the smaller the number before it, the better the low-temperature fluidity of the engine oil, and the better the protection for the engine during cold starts. For example, "5W" represents a minimum external temperature resistance of -30°C. 2. The number after "W" represents the viscosity of the engine oil at 100°C. The larger the number, the higher the high-temperature viscosity of the engine oil. Higher viscosity means the engine oil can better adhere to the surface of components, providing better protection for the engine during operation (engine operating temperatures can easily reach 100°C).