How are the grades of automotive engine oil classified?
2 Answers
Engine oil grades are classified based on their quality levels. This standard uses the letter "S" to represent oil for gasoline vehicles, with different grades of oil arranged alphabetically after the letter "S". The specific classifications and explanations of engine oil are as follows: Standalone letters: The "S" series represents oil for gasoline engines, with specifications including: SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL. The "C" series represents oil for diesel engines, with specifications including: CA, CB, CC, CD, CE, CF, CF-2, CF-4, CG-4, CH-4, CI-4. Coexistence: When both "S" and "C" letters are present, it indicates that the oil is suitable for both gasoline and diesel engines. From "SA" up to "SL", each subsequent letter indicates better performance than the previous one, with more additives in the oil to protect the engine. The later the letter in the alphabet, the higher the quality grade, and most international brands have oil grades above SF.
The grade of motor oil is primarily distinguished by numbers and letters. For SAE-labeled oils, such as 5W-30, the 'W' stands for winter temperature fluidity, where a smaller number indicates thinner oil at low temperatures, easier flow, and smoother starts. The number after, like 30, indicates thicker oil at high temperatures, protecting the engine from wear. This affects fuel efficiency and protection. If your car often operates in cold regions, choosing a lower W number can reduce startup difficulties. Another standard is API, such as API SN or SP, with SP being the latest grade, offering better environmental protection and cleaning power to reduce carbon buildup. Check your user manual and avoid switching grades arbitrarily to prevent engine damage. I recommend regular oil changes and selecting the right grade to extend engine lifespan.
