What is the difference between SL-grade and SN-grade engine oil?
2 Answers
SN-grade engine oil and SL-grade engine oil differ in quality level and phosphorus content requirements. Difference in quality level: SN-grade engine oil has the highest quality level among engine oils, and it is generally used in high-end cars. SL-grade engine oil belongs to the upper-middle quality level, and it is usually chosen for relatively good cars. Difference in phosphorus content requirements: The phosphorus content requirement for SL-grade engine oil is only no more than 0.1%. SN-grade engine oil has particularly high requirements for phosphorus content, even to the point of being phosphorus-free.
I've been driving for over a decade and have used many types of engine oil. SL and SN are two different standards for engine oil. The SN grade is newer and pays more attention to protecting the engine's emission system, such as components like the catalytic converter. It has a lower phosphorus content, which reduces air pollution from exhaust emissions. Additionally, SN oil has stronger cleaning performance, preventing carbon buildup inside the engine. SL is an older standard and is cheaper, but over time, it can lead to carbon deposits clogging the small oil passages. If your car is a newer model with a turbocharger or direct fuel injection, it's recommended to use SN-grade oil. However, older cars can still use SL without issues—the most important thing is to change the oil on time. My neighbor's 15-year-old car runs smoothly with SL-grade oil.
