What is the difference between 5w40 and 10w40 motor oil?

[DelOmar]

5w40 indicates that the oil can withstand external low temperatures of -30°C and external high temperatures of 40°C; 10w40 means the oil can tolerate external low temperatures of -25°C and external high temperatures of 40°C. Specific details are as follows: 1. The smaller the number before the W, the lower the low-temperature viscosity, the better the low-temperature fluidity, and the lower the applicable minimum temperature. The larger the number after the W, the higher the viscosity and the higher the applicable maximum temperature. 5w40 has a lower viscosity than 10w40. 2. During the winter months, cars may require one to two oil changes depending on mileage. The oil chosen for these changes must perform better than oils used in other seasons to ensure smooth driving in cold weather and provide optimal engine protection. When the weather warms up, you can switch to a lower-grade oil. Good motor oil should be selected based on the SAE viscosity index and API quality rating. When changing oil, pay attention to the labels on the packaging.