How are oil grades classified?
2 Answers
The classification of oil grades: gasoline type, diesel type, and gasoline-diesel universal type. Those starting with the letter S represent oils for gasoline engines, with specifications including: SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, SN; Those starting with the letter C represent oils for diesel engines, with specifications including: CA, CB, CC, CD, CE, CF, etc. The further back the letter after S or C, the higher the quality grade of the oil, indicating more stable performance and a higher oil grade. Currently, the market also divides oils into three categories: mineral oil, semi-synthetic oil, and synthetic oil, with corresponding oil grades as follows: SA to SJ are mineral oils, SJ and SL are semi-synthetic oils, and SM and SN are full synthetic oils.
I have a thorough understanding of motor oil grading systems, which mainly consist of viscosity and quality standards. The viscosity follows the SAE standard, such as 5W-30. The 'W' stands for winter low-temperature fluidity, and the smaller the number before it, the smoother the engine starts in cold weather—for example, 0W performs better than 5W in freezing conditions. The number after, like 30, indicates high-temperature viscosity; a higher number such as 40 offers better engine protection in hot climates. The quality grade follows the API standard, where SP is superior to SN, providing better cleaning and wear protection. With over a decade of driving experience, I initially neglected these details and used non-spec oils, leading to rapid engine carbon buildup and higher fuel consumption. Later, I learned to check the owner’s manual for viscosity matches—older cars might need 10W-40—and consider driving habits, opting for higher viscosity for frequent highway driving. Choosing the right oil extends engine life and saves money. Regular maintenance is also crucial; typically, check the oil grade every 5,000-8,000 kilometers.
