Can 10w40 engine oil be used in winter?

[DiElliott]

10w40 engine oil can be used in winter, but it depends on the minimum winter temperature in the region where the vehicle is used. This can be understood by examining the specifications of 10W40 engine oil. Below is an expanded explanation: 1. Firstly, the number 10 represents the low-temperature startup performance indicator. The smaller the number, the better the low-temperature startup performance. A value of 10 indicates that the oil can ensure normal startup at -25°C. The "W" stands for "Winter," indicating that this oil is suitable for winter use. The number 40 represents the oil viscosity—the higher the number, the greater the viscosity, and the better the high-temperature performance and high-temperature shear resistance. Therefore, whether to use this type of oil depends on the minimum temperature in the region where the vehicle is located. 2. The American Petroleum Institute (API) has established a standard for labeling engine oils, typically using formats like 5W-30 or 0W-40. This labeling is divided into two parts: the part after the hyphen "-" represents the oil's high-temperature shear resistance at 100°C and also indicates the base viscosity of the oil. A higher number means greater shear resistance, thicker oil film, higher base viscosity, and poorer fluidity. Conversely, a lower number means lower shear resistance, thinner oil film, lower base viscosity, and better fluidity. The "W" before the hyphen stands for "Winter" and represents the oil's low-temperature fluidity, i.e., low-temperature startup performance. The smaller the number before the "W," the better the low-temperature fluidity and startup performance. Subtracting 35 from the number before the "W" gives the minimum startup temperature for that oil viscosity. For example, 5W indicates a minimum startup temperature of -30°C. From the above explanation, 40 has a higher base viscosity, while 30 has a lower base viscosity. The difference between 10W and 15W is that 10W has a minimum startup temperature of -25°C.