What is the difference between SL and SN engine oil?
3 Answers
The differences between SL and SN engine oil are as follows: 1. Differences in oxidation resistance and wear resistance. Under high-temperature and high-speed operating conditions, SN has better high-temperature detergency than SL, making it especially suitable for turbocharged engines. SN-grade engine oil offers higher oxidation stability and wear resistance. Since SN engine oil contains lower levels of phosphorus and zinc compared to SL, it reduces wear on the three-way catalytic converter. 2. Different environmental protection levels. Engine oils are classified by environmental protection levels, with later letters indicating higher environmental standards. SL engine oil has a lower environmental protection level than SN, and SN-grade engine oil has the highest environmental protection level. 3. Different quality levels. Engine oils can be categorized by quality levels such as SG, SH, SJ, SL, SM, and SN, so SN is of higher quality than SL.
I've just researched this motor oil specification issue. The biggest difference between SL and SN lies in the environmental standards, with SN being an upgraded version introduced in 2010 that imposes stricter limits on phosphorus content. Don't underestimate this change - reduced phosphorus can extend the lifespan of catalytic converters. From my repair experience, older SL oil is more suitable for pre-2010 vehicles, while newer turbocharged cars run more reliably with SN oil due to its superior high-temperature sludge resistance. Specifically, SN oils use more calcium-based detergents to replace zinc-phosphorus additives in their formulation, which provides excellent low-temperature sludge prevention for direct injection engines. I remember last year a customer's German car triggered warning lights after just 5,000 kilometers due to using the wrong oil.
The small label difference on engine oil packaging is actually quite crucial. The SN grade passes two additional engine test benches compared to SL, especially regarding turbocharger deposit control. From disassembled engines I've observed, pistons using SN-standard oil show significantly cleaner undersides. Another detail is oxidation stability - SN oil lasts 30% longer under aggressive driving conditions. However, SL isn't unusable; it works perfectly fine for older naturally aspirated engines. Always check your owner's manual - my decade-old car continues using SL, but my neighbor's new hybrid strictly requires SN.
