How are the grades of automotive engine oil classified?

[OliveLynn]

Oil grades are classified based on the quality level of the oil, with the standard using the letter "S" to represent oil for gasoline vehicles. Different grades of oil are then arranged in alphabetical order after the letter "S". The specific classification and explanation of oil grades are as follows: 1. When letters exist alone: 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. 2. When both letters exist: 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 successive letter indicates that the oil's performance is superior to the previous one, with more additives included to protect the engine. The further the letter is in the alphabet, the higher the quality grade. Most international brands have oil grades above SF.