What Do Engine Oil Codes Mean?
2 Answers
The meaning of engine oil codes is as follows: Engine oil codes are divided into two categories, one is the oil viscosity, and the other is the oil grade. (1) Viscosity index: Generally, the SAE standard is used as the international standard, which is what we commonly refer to as 5W-20, 5W-30. The specific meanings are: The first number represents the low-temperature viscosity index, indicating the minimum working temperature at which the oil can function. (2) Grade index: In China, the API standard is generally used, divided into API SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, SN, SP; 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 suitable for both gasoline and diesel engines. This involves the oil's quality, shelf life, impurity content, etc. The later the grade, the higher the level, the better the quality, and the more expensive it is. This is what is commonly referred to as the standard for full synthetic and semi-synthetic oils. Generally, oils before SL are mineral oils, SM is semi-synthetic oil, SN and above are full synthetic oils, with the current highest grade being SP. Additionally, the European ACEA (European Automobile Manufacturers' Association) has established another set of standards, which are more stringent.
I did some research on this when choosing engine oil before. The oil codes like '5W-30' are actually quite scientific with their letter and number combinations. The 'W' at the beginning stands for winter, indicating low-temperature performance; the smaller the number before it, the smoother the cold starts. When I lived up north, I used 0W oil, and it started fine even at minus twenty degrees. The number after, like '30', is the high-temperature viscosity index – if you're doing long highway drives in summer, a higher number protects the engine better. You should check your car's manual for recommendations. My old Japanese car uses 30, while my friend's German car requires 40. The additive formulas vary between codes too, and the difference in performance under high-temperature, high-load conditions is quite noticeable.
