The number 40 represents the high temperature viscosity grade of engine oil. The higher the value, the stronger the high-temperature viscosity of engine oil, the thicker the oil film, and the better the sealing performance and protection ability.
Numbers 5 and 10 represent the lowest applicable temperature of engine oil, or low-temperature fluidity. 0 indicates that the minimum applicable temperature of engine oil is minus 35 degrees, and 5 indicates that the minimum applicable temperature of engine oil is minus 30 degrees.
If the lowest temperature of your car is above minus 35 degrees in winter, 5w-40 and 0w-40 have exactly the same effect on your car.