What Does the Oil Grade Mean?
2 Answers
The meaning of the oil grade is: it indicates viscosity and quality. The oil grade consists of two parts: classification and viscosity specification. "W" stands for winter, and the smaller the number before it, the better the low-temperature fluidity of the oil, representing a lower usable environmental temperature and better protection for the engine during cold starts. The number after "W" (after the hyphen) indicates the oil's high-temperature resistance; the larger the number, the better the oil's protective performance at high temperatures. Oil classification is represented by 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 without SI). Each subsequent letter indicates better performance than the previous one, with more additives to protect the engine; the later the letter, the higher the quality grade. Most international brands have oil grades above SF. The "C" series represents oil for diesel engines. If both "S" and "C" are present, it means the oil is suitable for both gasoline and diesel engines.
Engine oil viscosity grades are like your car's 'ID number,' telling you how it performs under different temperatures. Numbers like 5W-30—the 'W' stands for winter viscosity, where a lower number means smoother oil flow in cold weather. The second number indicates high-temperature viscosity; a higher value means better engine protection in hot conditions. Why does this matter? Choosing the wrong viscosity can lead to faster engine wear, hard starts, or poor fuel efficiency. When I change my oil, I always check the manual because requirements vary by model. In winter, it's best to use oil with a lower 'W' number, while a higher one is preferable in summer. Regularly checking the oil grade extends engine life and ensures smoother driving—don’t cut corners to save money.
