What does SN represent in engine oil?
2 Answers
Engine oil SN represents the highest grade of engine oil, which generally falls under the category of fully synthetic oil. Below are the functions of engine oil: Lubrication and friction reduction: Forms an oil film on the surfaces of two sliding components to prevent friction during operation, ensuring smooth movement of parts. Cleaning and dispersion: High-quality engine oil can flush away dirt on component surfaces through oil flow, adsorb tiny metal fragments inside the engine, and then scrape them into the oil pan via the piston oil ring. Cooling and temperature reduction: The engine generates high temperatures during operation. When the oil reaches the operating parts, it absorbs heat and carries it away, aiding in the cooling of components. Sealing and leak prevention: Forms a seal between the piston ring and piston via an oil film to prevent combustion exhaust gases from entering the crankcase. Corrosion and rust prevention: High-quality engine oil adheres to component surfaces, preventing contact with air, acidic substances, and harmful gases, thus protecting the engine from corrosion by atmosphere and water. Shock absorption: When the pressure at the engine cylinder port increases suddenly, the load on the piston, piston ring, connecting rod, and crankshaft bearings becomes significant. This load is transmitted and lubricated through the bearings, cushioning the impact load.
The SN designation represents the quality grade set by the American Petroleum Institute (API) for gasoline engine oils, indicating their performance standards. The 'S' prefix specifically denotes oils for gasoline engines, while the following 'N' is the specific grade code, ascending sequentially from SA to SP. Introduced in 2010, SN-grade engine oils impose stricter requirements for engine protection, such as a 40% improvement in high-temperature deposit resistance, making them particularly suitable for turbocharged models. When selecting engine oil, don't just focus on viscosity ratings; the SN grade ensures oil cleanliness and oxidation resistance, preventing engine carbon buildup and wear. While newer vehicles often use the higher SP standard, SN-grade oil is perfectly adequate for older cars.
