How are the grades of automotive engine oil classified?

[DiWalter]

Engine oil grades are classified based on their quality levels. This standard uses the letter "S" to represent oil for gasoline vehicles, with different grades of oil arranged alphabetically after the letter "S". The specific classifications and explanations of engine oil are as follows: Standalone letters: The "S" series represents oil for gasoline engines, with specifications including: SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL. The "C" series represents oil for diesel engines, with specifications including: CA, CB, CC, CD, CE, CF, CF-2, CF-4, CG-4, CH-4, CI-4. Coexistence: When both "S" and "C" letters are present, it indicates that the oil is suitable for both gasoline and diesel engines. From "SA" up to "SL", each subsequent letter indicates better performance than the previous one, with more additives in the oil to protect the engine. The later the letter in the alphabet, the higher the quality grade, and most international brands have oil grades above SF.