What is the difference between SL and SN grade engine oil?
2 Answers
The differences between SL and SN grade engine oil are introduced as follows: 1. Classification by quality grade. According to the API standard classification, from "SA" to "SP", each subsequent letter indicates an improvement in the oil's performance, surpassing the previous one. Currently, SP is the highest grade of engine oil, with SN being second only to SP. 2. In terms of performance. SN grade engine oil is of better quality than SL. 3. From a price perspective. Higher-grade oils are definitely more expensive, and SN grade is certainly more costly than SL grade. 4. In terms of characteristics. SN grade engine oil mainly improves in terms of high-temperature cleanliness. In comparison, SL grade oil does not have very high high-temperature cleanliness, and the SL grade does not have strict requirements on phosphorus content, only requiring it to be no higher than 0.1%. Turbocharged engines have very high requirements for engine oil, making SN grade oil more suitable for them.
I've been driving for over a decade and often check specifications when changing engine oil. Both SL and SN are API service classifications, but SL was the standard in the 2000s, while SN is newer and became popular around 2010 onwards. The key difference lies in composition: SL has higher phosphorus content which can clog catalytic converters and affect exhaust purification; SN reduces phosphorus and adds better additives to more effectively prevent sludge buildup, especially protecting engines under high temperatures. After switching to SN, I noticed significantly reduced engine noise and smoother cold starts in winter. If you drive newer vehicles or prioritize performance, SN is absolutely recommended; SL might suit older cars better, but avoid prolonged use as it can accelerate engine component wear. Choosing the right oil during regular maintenance can extend engine life by several years.
