How to Identify the Grade of Engine Oil?
3 Answers
Identifying the grade of engine oil is as follows: 1. API quality classification: The "S" series represents oil for gasoline engines. The "C" series represents oil for diesel engines. When both "S" and "C" letters are present, it indicates that the oil is suitable for both gasoline and diesel engines. 2. SAE viscosity classification: 10W-40 is its SAE standard viscosity value. The viscosity value first indicates that this oil is a multi-grade oil. "W" stands for WINTER, and the number before "W" represents the flow performance at low temperatures. The smaller the number, the better the starting performance at low temperatures. The number after "W" represents the stability of the oil at high temperatures (i.e., the possibility of thinning). The larger the number, the better the high-temperature stability performance of the oil.
I often help change the engine oil for our family car, and distinguishing the grades is actually quite simple—mainly by checking the label parameters on the bottle. The key lies in the SAE viscosity code, such as the format 5W-30. The first number, like 5, indicates low-temperature fluidity—the smaller the number, the smoother the engine starts in cold weather. The latter number, 30, represents high-temperature viscosity—the higher the number, the better the engine protection under hot conditions. Additionally, there’s the API rating, such as SP or SN, where SP is the latest standard, offering better cleaning and environmental performance. Regularly checking these ensures the oil is suitable for the vehicle, preventing premature engine wear and saving fuel costs. Just remember: use high-performance oil for new cars and basic oil for older cars—don’t mix them up.
As someone who maintains my car year-round, I believe the key to identifying oil grades lies in understanding those codes. In the SAE classification, the number before 'W' (like 0W) indicates better cold-weather starting capability, while the number after (e.g., 40) represents stronger high-temperature protection - this directly impacts engine durability. For API standards like CI-4 or SP, higher numbers indicate superior performance suitable for modern engines, preventing carbon buildup and pollution. At the shop, I always advise friends to cross-reference their vehicle manual when selecting oil - don't just consider price, as using the wrong grade can lead to increased fuel consumption and engine knocking. Always check the bottle label before refilling for peace of mind and safety.
