How are full synthetic engine oil grades classified by level?
4 Answers
Currently, full synthetic engine oils are mainly classified as SN grade. The API on engine oil stands for the American Petroleum Institute, and it is divided into grades SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, and SN, with the grade increasing in order. SN grade is currently the highest level of engine oil. SJ was the standard in the 1990s, SL was the standard in 2001, SM was the standard in 2004, and SN became the standard in 2010. Semi-synthetic engine oils are mainly classified as SL, SM, and SN grades, with SN grade being more common. However, synthetic engine oil represents the highest grade, with SN grade as the benchmark. The difference between full synthetic and semi-synthetic engine oils lies in the fact that full synthetic oil can operate over a wider temperature range, has a longer service life, and is more expensive. For the same oil film requirements, full synthetic oil can achieve the desired performance with lower viscosity, whereas semi-synthetic oil requires a relatively higher viscosity to meet the same requirements. In the same working environment, full synthetic oil has a much longer service life compared to semi-synthetic oil, making it more costly. However, when considering the reduced frequency of oil changes, the overall cost is not significantly higher. There is no uniform standard for the color of full synthetic engine oil. High-quality oil appears as a translucent yellowish-brown. If the oil contains water, it turns brown. After the engine has been running for a while, the oil may appear milky white with foam. Black oil usually indicates excessive sludge and iron particles or too much carbon in the oil. To check the oil's condition, pull out the dipstick and observe the scale marks against a light source. If the marks are not clearly visible through the oil on the dipstick, it means the oil is too dirty and needs to be replaced immediately.
The classification of fully synthetic oil grades is primarily determined by the API standard, established by the American Petroleum Institute. A newer letter suffix indicates a higher grade. For example, among the 'S' series, from SM and SN to SP, SP is newer than SN, offering better performance, improved environmental friendliness, and fuel efficiency. There's also the SAE viscosity grade, like 5W-30 or 0W-20. A smaller number before the 'W' indicates smoother cold starts, while a larger number after 'W' means better high-temperature protection, but this doesn't directly affect the grade level. As an experienced driver who has changed oil countless times, I've found that higher-grade oils like SP can reduce engine carbon buildup and extend the oil change interval to over 10,000 kilometers. When choosing, check your car's manual for the recommended standard instead of blindly opting for expensive options. Regular oil changes are key to maintenance, saving money and protecting your car. In summary, a newer API sequence number is a mark of high-end quality.
The grade of fully synthetic oil depends on the API sequence number, with higher letters after 'S' indicating better quality. SP is currently the top tier, newer than SN and with stronger environmental protection features. SAE viscosity, such as 10W-40, is another classification affecting flow and protection. My experience from years of car repair shows that higher-grade oil offers better wear resistance, quieter engine operation, and extends component lifespan. Remember not to just look at the numbers on the packaging; confirm the match between API and viscosity. Using high viscosity oil in hybrid models may be wasteful. For regular oil changes, it's recommended that owners check oil quality every 8,000 kilometers. Choosing higher API grades can also save some fuel consumption, making it more cost-effective in the long run. Though a small detail, it's crucial for car care.
The ranking of oil grades is straightforward: the newer the API standard letter, the higher the grade, for example, SP is better than SN. Viscosity labels like 5W-30 only affect temperature adaptability and do not indicate quality levels. I was confused when I first became a car owner, but I learned a bit after consulting the 4S shop. Higher-grade oils provide better engine protection and reduce friction noise. Remember to choose based on your car's needs; buying the most expensive isn't always necessary. Think of it this way: regular maintenance is key.
