Can 15w40 Engine Oil Be Used in Winter?
3 Answers
Whether 15w40 engine oil can be used in winter depends on the temperature conditions of the local winter and summer seasons. The specific judgment method for whether 15w40 engine oil can be used in winter is as follows: 1. 15W40 engine oil is suitable for use in temperatures above -20℃. Since engine oil has a certain freezing point and viscosity, i.e., an applicable temperature range, and the winter temperatures vary significantly between regions such as northern and southern China, the usability of 15W40 engine oil depends on the local winter and summer temperature conditions. 2. 15w40 engine oil can be used in southern regions during winter, but it is not suitable in northern areas like Harbin where temperatures are much lower. 3. The meaning of 15W40: The number before the W indicates the low-temperature fluidity of the engine oil, or the minimum applicable temperature. The smaller the number, the better the low-temperature fluidity and the lower the applicable minimum temperature. 15 indicates that the minimum applicable temperature is -20℃, and its low-temperature fluidity is relatively average. 40 represents the viscosity value of the engine oil, which is a relatively high-viscosity oil with good high-temperature protection performance.
I've been driving for over a decade and have used various engine oils. 15w40 can be used in winter, but it depends on the climate. In southern regions or areas where temperatures rarely drop below -10°C, like where I live in Shanghai, it's fine for winter use—cold starts might be a bit slower but manageable. However, in extremely cold northern areas like Harbin, at -20°C, the car might not start because the oil is too thick with poor fluidity, making engine ignition difficult and increasing component wear. I recommend checking the ambient temperature; if it's consistently low, switching to 5w40 or 0w40 is better. Engine oil protects the engine by flowing properly—excessive viscosity increases fuel consumption and carbon buildup risk, and in severe cases, jump-starting may be needed. The cost of changing oil isn't high, but it's much safer. Also, refer to the vehicle manual—some brands require specific viscosity grades, so following the manufacturer's instructions is always correct.
I personally used 15w40 engine oil during mild winters, such as when temperatures were around zero degrees Celsius, and the engine started relatively smoothly. However, one year when a cold snap suddenly dropped temperatures to -15°C, the car took a long time to start. Later, a mechanic explained that the oil's low-temperature fluidity was too poor, providing insufficient engine protection in winter. He recommended switching to a lower viscosity oil like 5w for winter use. The oil rating system indicates that "W" stands for winter, and a lower number before the W means better cold-weather flow. Using 15w oil in extremely cold regions carries significant risks, potentially making the engine hard to start or even causing damage. Now, my car uses 5w40 oil in winter, which ensures quicker starts and better fuel efficiency. Additionally, it's important to monitor oil change intervals and temperature changes. If you insist on using 15w40 oil, make sure to park the car indoors to keep it warm and avoid prolonged exposure to low temperatures. It's best to check the oil condition before winter arrives—don't compromise safety for convenience.
