Is 15W40 Oil Suitable for All Seasons?
2 Answers
Generally, 15W40 is considered an all-season oil that can be used throughout the year. When used correctly, 15W40 oil will not harm the engine. More information about 15W40 oil is as follows: 1. 15W40 oil is suitable for use in temperatures above -20°C. Since oil has a certain freezing point and viscosity, which determine its applicable temperature range, and considering the significant temperature differences between the north and south of China in winter, the suitability of 15W40 oil depends on the local temperature conditions in both summer and winter. 2. The meaning of 15W40: The number before the W indicates the oil's low-temperature fluidity, or the minimum temperature at which the oil can be used. The smaller the number, the better the low-temperature fluidity and the lower the minimum applicable temperature. 15 indicates that the oil can be used at a minimum temperature of -20°C, but its low-temperature fluidity is relatively average. 40 represents the oil's viscosity value, indicating that it is a relatively high-viscosity oil with good high-temperature protection performance.
I've been working in car maintenance for many years and often get asked if 15w40 oil can be used year-round. Actually, it depends on where you use your vehicle. The '15w' in the oil represents its winter low-temperature fluidity. The number 15 means the viscosity is higher during cold starts, and it may not flow smoothly below freezing, especially in extremely cold regions like Northeast China where temperatures can drop to -20°C in winter, making starting difficult. The '40' refers to high-temperature viscosity, which provides excellent engine protection during long summer drives. So in warmer regions like South or East China, where winters rarely freeze, 15w40 can be used all year round, offering both convenience and cost savings. However, if you live in colder areas like Xinjiang or Inner Mongolia, it's better to switch to 5w30 in winter for smoother cold starts and better wear protection. In short, checking your vehicle's manual and local temperatures is a wise choice—don't compromise safety for minor savings.
