How are oil grades classified?
2 Answers
Oil grade classification methods: S represents oil for gasoline engines, C represents oil for diesel engines. Then, following the English alphabetical order after the letters S and C, from SA to SL, the later the English letter appears in the alphabet, the higher the oil grade, indicating better performance of the oil. The S series represents oil specifications for gasoline engines: SA, SB, SC, SD, SE, SF, SG, SH. The C series represents oil specifications for diesel engines: CA, CB, CC, CD, CE, CF, CF2, CF4, CG4, CH4, CI4. When both S and C letters are present, it indicates that the oil is suitable for both gasoline and diesel engines. Oil is the lubricant used by engines, composed of base oil and additives.
As a veteran driver with twenty years of experience, let me talk about the tricks in engine oil. The grading of engine oil mainly depends on the API rating, such as the common SP and SN letter combinations nowadays—the further back the letter, the newer the oil. Then there’s the SAE viscosity, like 5W-30. The number before the W represents low-temperature fluidity (5W handles cold better than 10W), while the numbers 30 or 40 after it indicate high-temperature protection. I’ve been using 5W-30 in my car year-round, and even at minus twenty degrees in winter, the engine starts without a hitch. Recently, I heard that China VI vehicles now require low-ash engine oil to prevent clogging the particulate filter.
