Can 10w40 engine oil be used in winter?

[VonRemington]

10w40 can be used in winter. 10w40 engine oil is generally suitable for temperatures ranging from -25°C to 40°C. In southern regions, engine oil with a viscosity grade of 30 is commonly used; in northern regions, 10W or 15W engine oil is required, and in extremely cold areas, 5W oil may be necessary. The specific details of 10w40 engine oil are as follows: Meaning of 10w: The number 10 represents the low-temperature startup performance indicator. The smaller the value, the better the low-temperature startup performance. A value of 10 indicates that the oil can ensure normal startup even at -25°C. The letter W stands for Winter, indicating that this oil is suitable for winter use. Meaning of 40: The number 40 represents the oil viscosity. The higher the value, the greater the oil's viscosity, and the better its high-temperature kinematic viscosity and high-temperature shear resistance.

[VonRose]

I've seen quite a few car owners still using 10W40 oil in winter. Actually, this depends on the temperature. The 'W' in 10W stands for winter, and the number 10 represents the temperature at which the oil can still function in cold weather, roughly down to about -25°C, but the actual performance is influenced by many factors. If your car is parked outdoors in winter and the local temperature occasionally drops below freezing, like in some less cold areas of North or Northeast China, 10W40 might still work. But if the temperature drops to -30°C at night, the oil's fluidity decreases, causing the engine to make gurgling noises during startup due to insufficient lubrication. This can lead to internal engine wear and even make it harder to start. I suggest everyone check the weather forecast in advance. If winter temperatures often drop below -20°C, it's better to switch to a lower W-rated oil like 5W40 or 0W40, which have better fluidity and can protect the engine. Of course, oil should also be changed regularly; otherwise, even the best grade won't help.

[SanPatrick]

From the perspective of my family car, can 10w40 be used in winter? I've tried it several times. I live in the south, where winter temperatures typically range from a few degrees below zero to above zero. Last winter, I used 10w40 oil throughout the season, and the engine started without major issues, except for a slight delay during cold starts in the morning—it took about two extra seconds to ignite. However, once running, everything was normal. But when I traveled to northeastern China for work last year and temperatures suddenly dropped to -25°C, the car struggled a bit. The engine made strange noises during startup, so I quickly switched to 5w40 oil, and it ran much smoother. Therefore, I think the key is to consider where you live and the lowest temperatures you encounter. If winter temperatures mostly stay above -10°C, 10w40 is quite suitable. But if you're in an extremely cold region, don't push it—upgrade the oil grade or preheat the car before driving to avoid engine damage or the risk of breaking down mid-trip.

[LaChloe]

As someone who has been driving in areas with large temperature differences for a long time, I have to say that using 10w40 in winter really depends on the weather. For example, in the Yangtze River Delta region, where winter temperatures rarely drop below freezing, 10w40 is perfectly fine, and the oil's fluidity can still be maintained. However, in northern regions like Inner Mongolia or Heilongjiang, where temperatures often drop to -30 degrees Celsius, 10w40 can't handle it. Poor fluidity can lead to increased engine wear during cold starts. Last winter, when I drove to the north without changing the oil, I had difficulty starting the engine halfway. The mechanic later told me that some parts were damaged as a result. Therefore, the suitability of 10w40 depends on the extreme low temperatures. It is recommended that car owners check the historical minimum winter temperatures in their local area. If it is below -20 degrees Celsius, upgrading to a 5w or 0w series would be safer.

[DeMaximus]

I've used 10W40 oil in winter, but must warn everyone about the considerable risks. In mild winters around -10°C, it might still work, though poorer flow reduces engine efficiency and slows startup. If temperatures consistently drop below -20°C, the risk of insufficient engine lubrication increases significantly, potentially causing premature component wear or higher failure rates. Once on an older car with 10W40 in extreme cold, it nearly failed to start—luckily addressed in time to avoid major issues. So regularly check oil condition and vehicle status, keep low-temperature oil handy in cold weather, or switch to the appropriate grade beforehand to ensure safe and smooth driving.