What Does the Oil Grade Mean?
2 Answers
The meaning of the oil grade is: The oil grade usually indicates viscosity and quality. The viscosity of lubricating oil is often identified using SAE (Society of Automotive Engineers) grades. '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' represents the oil's high-temperature resistance; the larger the number, the better the oil's protective performance at high temperatures. Oil grades are classified using a combination of two letters. The 'S' series represents oil for gasoline engines, with specifications generally ranging from SA to SN (in alphabetical order, but excluding SI). Each subsequent letter indicates improved oil performance, with more additives to protect the engine. The later the letter in the alphabet, the higher the quality grade. Among international brands, most oil grades are SF or higher.
Engine oil grades are primarily classified by SAE viscosity ratings, such as the common 5W-30. The 'W' stands for Winter, and the lower the number before it, the better the oil's low-temperature fluidity. For example, 5W indicates it can flow normally even in sub-zero temperatures, preventing cold-start difficulties. The number after, like 30, represents high-temperature viscosity—the higher the number, the thicker the oil in hot conditions, protecting engine components from wear. As I always emphasize when repairing cars, choosing the right grade is crucial: older cars or those in hot climates should use higher viscosity oils like 40, while colder weather calls for lower 'W' numbers to ensure smooth starts. Using the wrong oil can increase fuel consumption, cause sluggish acceleration, or even engine damage. New car owner manuals specify recommended grades—stick to them and avoid arbitrary changes. Checking the oil grade during annual oil changes can extend your vehicle's lifespan by several years.
