What is the difference between Mobil oil SN and SL?
3 Answers
The difference between Mobil oil SN and SL lies in their phosphorus content: Mobil oil SN contains no phosphorus, while SL contains no more than 0.1% phosphorus. The functions of engine oil are: 1. To reduce friction and high temperatures; 2. To minimize gas leakage and prevent contamination from external pollutants; 3. To protect components from contact with water, air, and harmful acidic gases; 4. To cushion the pressure rise in the engine cylinder port; 5. To clean dirt generated on the working surfaces of components. Signs that indicate the need for an oil change include: 1. Checking the oil viscosity—if there is no viscosity, the oil needs to be changed; 2. The oil color turns black; 3. Excessive black particles, metal shavings, or carbon deposits in the oil; 4. The oil has an unusual smell.
When I changed my engine oil last time, I did some serious research on Mobil's SN and SL grades. Both standards are set by the American Petroleum Institute (API). SN is the newer standard introduced in 2010, significantly more advanced than the SL from 2001. The biggest difference lies in environmental protection—SN reduces phosphorus content to below 0.08%, stricter than SL's 0.10%, specifically to prevent clogging the catalytic converter. Driving a turbocharged car, I've noticed a clear difference: SN oil results in noticeably less carbon buildup, and the engine sounds smoother. If you're driving a car from the last decade, especially those meeting China 5 or China 6 emission standards, you can't go wrong with SN—it's also more compatible with particulate filters. Using SL in older cars won't cause damage, but its protective qualities just don't keep up with modern engines.
After running this auto repair shop for so many years, I often get asked about motor oil ratings. The main difference between Mobil SL and SN lies in their formulation standards. Simply put, SN uses more advanced detergent dispersants specifically designed to address low-speed pre-ignition issues common in modern direct injection engines. From the many engines I've disassembled, pistons using SN oil show virtually no black carbon deposits at the bottom, while SL oil tends to leave some sludge buildup. Another often overlooked point is that SN has biodegradability requirements, making it more environmentally friendly. Currently, SL oils on the market are mostly leftover stock, as new products now start at SN grade, with SP grade already available. However, if you're driving an old Jetta from before 2005, using SL oil would still be perfectly fine.
