What is the classification of fully synthetic engine oil grades?
1 Answers
Currently, fully synthetic engine oil is mainly classified as SN grade. The API (American Petroleum Institute) designation on engine oil is divided into grades SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, and SN, with each subsequent grade representing higher quality. SN grade is currently the highest-level engine oil. SJ was the standard in the 1990s, SL in 2001, SM in 2004, and SN in 2010. Semi-synthetic engine oil is primarily classified as SL, SM, or SN grade, with SN being the most common. However, fully synthetic engine oil represents the highest grade, exemplified by SN grade. The difference between fully synthetic and semi-synthetic oils lies in the fact that fully synthetic oil can operate over a wider temperature range, has a longer service life, and is more expensive. For the same oil film requirements, fully synthetic oil can achieve the desired performance with lower viscosity, whereas semi-synthetic oil requires a relatively higher viscosity to meet the same standards. Under identical working conditions, fully synthetic oil lasts much longer than semi-synthetic oil, making it more costly. However, when considering the reduced frequency of oil changes, the overall cost is not significantly higher. There is no uniform standard for the color of fully synthetic engine oil. High-quality oil typically appears as a translucent yellowish-brown. If water is present in the oil, it turns brown. After the engine has been running for some time, the oil may appear milky white with foam. Black oil usually indicates excessive sludge, iron particles, or carbon deposits. To check the oil's cleanliness, pull out the dipstick and observe the markings under bright light. If the markings are unclear through the oil on the dipstick, the oil is too dirty and needs immediate replacement.
