What does the engine oil grade represent?

[LaAmy]

The engine oil grade represents the viscosity and quality of the oil. The viscosity of lubricating oil is often indicated using the SAE grade, where SAE is the abbreviation for the Society of Automotive Engineers. The 'W' stands for winter, and the smaller the number before it, the better the oil's low-temperature fluidity, indicating a lower usable environmental temperature and better engine protection during cold starts. The number after 'W' indicates the oil's high-temperature resistance; the larger the number, the better the oil's protective performance at high temperatures. The oil classification is represented by a combination of two letters. The 'S' series represents oil for gasoline engines, with general specifications ranging from SA to SN. Each subsequent letter indicates better performance than the previous one, with more additives to protect the engine. The further the letter is in the alphabet, the higher the quality grade.