What is the Classification of Engine Oil?

[Ophelia]

Below is a detailed introduction to the classification standards for engine oil grades: 1. Types of Engine Oil: Engine oil grades are divided into gasoline-type, diesel-type, and universal gasoline-diesel-type. Those starting with the letter "S" represent oils for gasoline engines, with specifications including API SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, SN. Those starting with the letter "C" represent oils for diesel engines, with specifications including API CA, CB, CC, CD, CE, CF, CF-2, CF-4, CG-4, CH-4, CI-4. If both are present, such as SM/CF, it indicates that the oil is universal for both gasoline and diesel engines. 2. Meaning of Letters: The further the letter after S or C, the higher the quality grade of the oil, indicating more stable performance and a higher oil grade. Currently, the market also categorizes engine oils into three types: mineral oil, semi-synthetic oil, and synthetic oil. Correspondingly, oil grades from SA to SJ are mineral oils, SJ and SL are semi-synthetic oils, and SM and SN are fully synthetic oils. In addition to the oil grade identification, some oil packaging may have the SAE label. SAE stands for the Society of Automotive Engineers, which sets the standard viscosity values for engine oils, such as 5W-30. 3. Numeric Codes: Numbers like 20, 30, 40, 50 alone indicate summer-use oils, with higher numbers representing higher viscosity and suitability for higher temperatures. Numbers followed by "W" indicate winter-use oils, such as 0W, 5W, 10W, 15W, 20W, 25W. The letter "W" stands for Winter, and the smaller the number before W, the lower the viscosity, better low-temperature fluidity, and suitability for lower temperatures. Codes like 5W-40, 10W-30, 15W-40 indicate all-season oils, suitable for a wide range of temperatures.