What is API Oil Classification?
3 Answers
API oil classifications include SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, and SN. Below is relevant information: API Introduction: API stands for the American Petroleum Institute, the first national-level commercial association in the United States and one of the earliest and most successful standard-setting trade organizations worldwide. The API oil standard refers to the specifications established by this institute for engine oils. API Letter Representation: In the API standard, the letter "S" denotes gasoline engines, while "C" represents diesel engines. The subsequent letters indicate the oil's classification level—the later the letter appears in the alphabet, the higher the grade and quality of the lubricant. Currently, SN is the highest classification for gasoline engine oils in the API standard.
When it comes to API oil grades, I think it's quite crucial. As someone who's been driving for over a decade, I always pay attention to it during maintenance. API is the oil quality standard set by the American Petroleum Institute, specifically used to evaluate oil quality. Grades like SN and SP are for gasoline engines, with higher grades indicating better cleaning and protection. I know SP is currently the mainstream grade—it effectively prevents deposits and wear inside the engine, improves fuel efficiency, and reduces noise. Choosing the right API grade affects engine longevity. For example, the S-series for gasoline engines and C-series for diesel engines shouldn't be mixed, as it may accelerate part wear. API and ILSAC standards are often used together, with ILSAC GF-6 corresponding to API SP, suitable for various vehicle models. I recommend checking the API mark on the bottle before purchasing and changing it regularly to avoid malfunctions, especially for highway driving where safety comes first—otherwise, engine issues can be much more troublesome to fix. In short, API grades are the basic guarantee of reliable oil quality and shouldn’t be taken lightly.
After repairing so many cars, I find the API oil classification system very practical. When we look at oil cans in the repair shop, we always check for API ratings like SN or SP first. The 'S' indicates oil specifically for gasoline engines, and the protection level depends on the rating—higher grades like SP can reduce carbon buildup and overheating risks. 'C' prefix oils are for diesel engines, such as CK-4. Using the wrong oil may cause engine knocking or sudden fuel consumption spikes. The API standard gets regular updates, with features like low-speed pre-ignition protection added from SN to SP. I've also noticed that API and ACEA standards complement each other, making them suitable for European cars. In practice, I recommend car owners choose the API grade specified in their manual and check the oil condition during maintenance—good oil can reduce repair frequency and save significant money.
