What does the gasoline engine oil label mean?

Pacific Auto Network gasoline engine oil label meaning: indicate the viscosity value of engine oil, such as SAE5W-30, where is it? W? Is for winter, w? The previous figure represents the flow viscosity at low temperature. The smaller this figure is, the better the low-temperature fluidity of the engine oil is, and the better the protection ability of the engine when the vehicle is cold started. ? W? The number behind is the viscosity of oil at 100℃, and the larger the number, the higher the viscosity.

The oil label includes two parts: classification and viscosity specification. Oil labels usually indicate viscosity and quality. W stands for winter, and the smaller the number in front of it means the better the low-temperature fluidity of the engine oil, which means that the lower the available ambient temperature, the better the protection ability of the engine during cold start; The number after "W" (after the horizontal line) is the index of high temperature resistance of oil. The larger the number, the better the protective performance of oil at high temperature.

The label after oil classification indicates its viscosity specification. For example, in "15W-40, 5W-40", "w" means winter. The smaller the number in front of it, the better the low-temperature fluidity of the oil, which means that the lower the available ambient temperature, the better the protection ability of the engine during cold start. For example, 5W means the external low temperature is -30? C, and the low temperature resistance of 20W is-15? The number after c.w represents the kinematic viscosity of engine oil at 100℃, and the higher the value, the higher the viscosity. 40 stands for 100℃, and the standard of kinematic viscosity is between 12.5mm2/s and 16.3mm2/s, which is definitely not used at 40℃ as some anecdotal statements say.

Oil classification is represented by a combination of two letters. The series starting with "S" stands for gasoline engine oil. The general specification is from SA to SN (in alphabetical order, without SI). Every time a letter is added, the performance of engine oil will be better than the previous one, and there will be more additives in engine oil to protect the engine. The lower the letter, the higher the quality grade, and most of the oil grades in international brands are above SF grade. The series starting with "C" stands for diesel engine oil. If the letters "S" and "C" exist at the same time, it means that this oil is a common type of gasoline and diesel. (Photo/Text/Photo: Pacific Auto Network Zeng Caihong)