What does SM5W30 engine oil mean?

[Hannah]

SM5W30 indicates that the engine oil quality grade is SM from the "S" series. Engine oil, also known as engine lubricant, serves functions such as lubrication, cleaning, cooling, sealing, and friction reduction for the engine. Engine oil consists of two parts: base oil and additives. The base oil is the main component of lubricating oil, determining its fundamental properties; additives compensate for and improve the shortcomings of base oil performance, making them an essential part of lubricating oil. In 5W30 engine oil, the "5" represents the low-temperature fluidity of the oil. The smaller the number, the lower the ambient temperature it can be used in, and the better the protection it provides for the engine during cold starts. The number 5 indicates resistance to external low temperatures of -30°C. The "30" represents the kinematic viscosity standard at 100 degrees Celsius, which is 30. This number indicates the oil's high-temperature resistance. The larger the number, the better the oil's protective performance under high temperatures. The symbol "W" stands for winter. The smaller the number before the W, the lower the low-temperature viscosity, the better the low-temperature fluidity, and the lower the minimum applicable temperature.