The "SN" part indicates the type and quality grade of the engine oil. S indicates that it is used in gasoline engines, and the corresponding letter is C for diesel engines. If both S and C are present, it means that it can be used in both gasoline and diesel engines. This article mainly describes the engine oil used in gasoline engines, and no further explanation will be given below. N indicates the quality grade of the engine oil. At this position, the common ones are J, L, M, and N. The later the letter order, the higher the quality. Obviously, N is the best.
The "5W-40" part is the viscosity mark of the engine oil, which is the most important reference mark for everyone to buy engine oil. The viscosity mark is divided into two parts: "before W" and "after -". Let's first explain the meaning of W. Here, W is not as variable as the SN above. It is always displayed as W. 0W means that it can be used at an outside temperature of -35℃, and 5W means that it can be used at -30℃. Obviously, this indicates low-temperature viscosity. Compared with 5W, 0W has better fluidity at ultra-low temperatures, lower viscosity, and a wider range of applicable low temperatures. It also consumes less fuel in winter. However, in most parts of my country, the difference between 0W and 5W is not very big. 0W is more recommended in the north. 0W and 5W are the most common marks on the market. 10W is rare (mainly in the lowest-end engine oil), and larger values are basically not seen.
The number after the horizontal bar indicates the viscosity under high temperature (after normal use of the engine), that is, high temperature resistance. Common ones on the market are 20, 30, and 40. 20 has the thinnest viscosity in a hot engine, and 40 has the highest viscosity. The advantage of low viscosity is high fluidity, fast throttle response, greater power, and more fuel economy; the disadvantage is poor lubrication and large engine wear. The opposite is true for high viscosity grades. As for which viscosity grade to choose, you can refer to the manual. If there is no clear indication in some manuals, you can refer to the grade used for maintenance at SSSS stores, or the certification of the car factory (which will be explained in detail later). But the general rule is: Japanese cars use 20 or 30, American cars use 30 (a few can use 20), German cars without turbochargers use 30, and German turbochargers use 40. It can be seen that 30 is the most universal, 20 is basically only for Japanese cars (a few American cars are also applicable), and 40 is almost exclusive to German turbochargers. Domestic brands basically use 30 the most. Have you found the coordinates of your car? SO EASY!
