At What Subzero Temperature Can 15w40 Engine Oil Not Be Used?
3 Answers
15w40 engine oil should not be used when the temperature is below -20°C. Low-temperature fluidity of engine oil: The number before the W indicates the low-temperature fluidity of the engine oil, which can also refer to the minimum applicable temperature of the oil. The smaller the number, the better the low-temperature fluidity and the lower the minimum applicable temperature. The number 15 indicates that the minimum applicable temperature is -20°C, and its low-temperature fluidity is relatively average. The number 40 represents the viscosity value of the oil, which is a relatively high-viscosity oil with good high-temperature protection performance. Using engine oil in winter: Since engine oil has a certain freezing point and viscosity, i.e., an applicable temperature range, and there are significant differences in winter temperatures between regions, such as between northern and southern China, this oil can be used in winter in southern regions of China but is not suitable in colder northern areas like Harbin.
In my years of driving experience, 15w40 engine oil basically becomes unusable when temperatures drop below -15 degrees Celsius. At this point, the oil thickens like syrup, making engine startup particularly difficult. I remember one winter in Northeast China at -20 degrees when the car simply wouldn't start - switching to 5w30 oil solved the problem. In such conditions, slow oil flow accelerates wear on pistons and bearings, potentially causing long-term engine damage and increased fuel consumption. It's advisable to check your oil type before cold seasons. If you're in northern regions or mountainous areas with low temperatures, switching to winter-grade oils starting with 5w or 0w is best to avoid roadside breakdowns affecting safety. Winter vehicle maintenance requires extra attention - don't lose big by skimping on small things. Timely oil changes can significantly extend your vehicle's lifespan.
I'm quite into studying motor oil knowledge. The low-temperature applicability of 15w40 is indeed limited. It's suitable for temperatures down to about -10°C, but if it drops below -15°C, the viscosity becomes too high, leading to poor pumpability. At this point, when starting the car, the oil flows slowly, causing the engine to run dry for a few seconds, which can damage internal components and potentially increase fuel consumption. Definitely avoid using it at -20°C; switching to 10w30 or a lower W-grade oil is the wiser choice. In daily driving, paying attention to weather forecasts and adjusting promptly is crucial. When selecting oil, refer to the vehicle manual to ensure it matches seasonal changes and protects engine performance.
