What does 5w-40 engine oil mean?

[Galadriel]

5w-40 engine oil means: 5 represents the fluidity of the oil, the smaller the number, the better the fluidity of the oil, and it also indicates the minimum temperature value that the oil can be applied to; w is the abbreviation of Winter; 40 represents the viscosity of the oil, the larger the number, the greater the viscosity of the oil, the better the high-temperature protection performance, and the greater the corresponding resistance. 5w-40 engine oil is suitable for electronically injected gasoline engines with crankcase ventilation devices and catalytic converters, as well as turbocharged intercooled direct-injection diesel engines with crankcase ventilation and exhaust gas recirculation devices, operating under various working conditions. Such engines usually operate under extreme temperatures and may have longer oil change intervals, which can put great pressure on the engine, leading to reduced engine sensitivity and performance degradation. The oil contains top-level power cleaning and dispersing technology, which, compared with traditional lubricating oil, can persistently prevent the formation of sludge and carbon deposits, effectively protect the engine, and significantly improve vehicle performance.