What Do the Numbers in Motor Oil Ratings Mean?

[AliceRose]

Motor oil rating numbers indicate the viscosity of the oil. The oil rating consists of two parts: the classification and the viscosity specification. The smaller the number before the letter, the better the low-temperature fluidity of the oil, meaning it can be used in lower environmental temperatures and provides better protection for the engine during cold starts. The number after the letter indicates the oil's high-temperature resistance; the higher the number, the better the oil's protective performance under high temperatures. Oil classification is represented by a combination of two letters. The "S" series represents oils for gasoline engines, with general specifications ranging from SA to SN (excluding SI). Each subsequent letter indicates improved performance over the previous one, with letters further in the alphabet representing higher quality grades. Most international brands have oil grades above SF. The "C" series represents oils for diesel engines. If both "S" and "C" letters are present, it means the oil is suitable for both gasoline and diesel engines.