What is the classification of fully synthetic engine oil grades?

[Jason]

Currently, fully synthetic engine oil is mainly classified as SN grade. The API (American Petroleum Institute) designation on engine oil is divided into grades SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, and SN, with each subsequent grade representing higher quality. SN grade is currently the highest-level engine oil. SJ was the standard in the 1990s, SL in 2001, SM in 2004, and SN in 2010. Semi-synthetic engine oil is primarily classified as SL, SM, or SN grade, with SN being the most common. However, fully synthetic engine oil represents the highest grade, exemplified by SN grade. The difference between fully synthetic and semi-synthetic oils lies in the fact 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 lower viscosity, whereas semi-synthetic oil requires a relatively higher viscosity to meet the same standards. Under identical working conditions, fully synthetic oil lasts much longer than 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 fully synthetic engine oil. High-quality oil typically appears as a translucent yellowish-brown. If water is present in the oil, it turns brown. After the engine has been running for some time, the oil may appear milky white with foam. Black oil usually indicates excessive sludge, iron particles, or carbon deposits. To check the oil's cleanliness, pull out the dipstick and observe the markings under bright light. If the markings are unclear through the oil on the dipstick, the oil is too dirty and needs immediate replacement.

[ElisaRose]

The classification of fully synthetic engine oil can be viewed from two perspectives. One is the SAE viscosity grade, such as 5W-30. The smaller the number before the W, the better the low-temperature fluidity, and the larger the number after the W, the stronger the high-temperature protection. For example, 0W-40 is considered a high-grade product with good overall performance. The other is the API performance grade, ranging from the earliest SA to the current SP. The later the letter in the alphabet, the higher the grade. SP-grade oil has much better cleaning and oxidation resistance capabilities than SN-grade. Some car manufacturers also have their own certification standards, such as Volkswagen's VW508. Oils that meet these special certifications are also considered high-grade. When choosing engine oil, don’t just look at the term 'fully synthetic.' You need to consider the viscosity, API grade, and the requirements in your car’s manual to determine the grade.

[KarterLynn]

I've researched this when changing engine oil before. The grade of full synthetic oil mainly depends on the labeling on the package. In terms of viscosity grades, 5W is suitable for temperatures as low as -25°C, while 0W can withstand -35°C, making it a higher grade. Performance grades are categorized by API standards, commonly SN, SP, etc. My car currently uses SP-grade oil, and I can clearly feel smoother cold starts compared to the previous SN-grade. Additionally, Japanese cars prefer low-viscosity 20-grade oil, while German cars recommend 40-viscosity oil, which reflects different orientation preferences in grades. If you see engine oil with ACEA European standard certification, such as C5 grade, it usually indicates a higher and more expensive grade. In short, don’t just look at the price; what truly matters is choosing the oil that best suits your car.

[MaxMarie]

The quality of fully synthetic engine oil is primarily determined by three factors. The SAE viscosity rating indicates fluidity, with lower numbers before the 'W' (Winter) being superior – 0W outperforms 5W in cold conditions. The API classification shows SP as the latest and best standard for protecting modern engines. Some oils also carry ILSAC certification, with energy-conserving labels indicating better performance. When selecting oil, don't assume all fully synthetic oils are equally good – always verify these three specifications against your vehicle's manual.