What are the different grades of fully synthetic engine oil?
2 Answers
"Currently, fully synthetic engine oil is mainly classified under the SN grade. The API (American Petroleum Institute) classification system includes grades such as SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, and SN, with each subsequent grade representing a higher quality. SN is currently the highest grade available. SJ was the standard in the 1990s, SL in 2001, SM in 2004, and SN in 2010. Semi-synthetic engine oil is primarily classified under SL, SM, and SN grades, with SN being the most common. However, fully synthetic oil is the highest grade, represented by SN. The main differences between fully synthetic and semi-synthetic oils are that fully synthetic oil can operate over a wider temperature range, has a longer service life, and is more expensive. For the same oil film requirements, fully synthetic oil can achieve the desired performance with a lower viscosity, whereas semi-synthetic oil requires a higher viscosity to meet the same requirements. In the same working environment, fully synthetic oil lasts much longer than semi-synthetic oil, making it more expensive initially. 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 fully synthetic engine oil. High-quality oil is typically a translucent yellowish-brown. If the oil contains water, it may appear brown. After the engine has been running for some time, the oil may turn milky white and develop foam. Black oil usually indicates excessive sludge, iron particles, or carbon deposits. To check the oil's condition, pull out the dipstick and observe the markings under bright light. If the markings are not clearly visible through the oil, it means the oil is too dirty and needs to be replaced immediately."
As a regular car owner who drives frequently, I know that full synthetic oils are classified under several mainstream standards. The most common is the API rating, where SP is the latest high-performance grade, while SN and SM are also commonly seen in older vehicles. They ensure cleanliness and anti-wear performance, which is crucial for engine protection. Viscosity grades like 0W-20 or 5W-30 are defined under the SAE standard, where lower numbers indicate better low-temperature fluidity, making them more suitable for driving in cold seasons. When choosing, it's essential to refer to the car's manual. Modern cars mostly use SP, but if budget is tight, SN is also acceptable and can save some money. I've also noticed that using full synthetic SP-grade oil can reduce fuel consumption and emissions, making daily commutes more eco-friendly and safer. It's recommended to change the oil once a year to maintain engine health. Overall, understanding these grades helps avoid incorrect oil changes and extends the car's lifespan, which I find quite practical for drivers.
