What Do the Numbers on Engine Oil Represent?

[LeKayden]

Taking SAE5W40 as an example, the viscosity of lubricating oil is often indicated using the SAE grade system. The letters and numbers in the code represent the following: "W" stands for Winter, and the smaller the number before it, the better the oil's low-temperature fluidity, indicating superior engine protection during cold starts. The number after "W" indicates the oil's high-temperature resistance; a higher number means better protective performance under high temperatures. Engine oil, also known as motor oil or engine lubricant, is a substance enhanced with additives in a base oil. It primarily contains anti-wear additives, detergents, dispersants, and multi-grade viscosity index improvers, and is used for lubricating internal combustion engines.