What does 15w40 mean for diesel engine oil?
2 Answers
15w40 represents the viscosity and low-temperature flow performance of engine oil. 15w indicates that the engine oil can flow normally at -20 degrees Celsius, while 40 represents the high-temperature viscosity of the engine oil. A 40-viscosity engine oil is considered relatively high in viscosity. The larger the number, the higher the viscosity of the engine oil. Here is more information about engine oil: The viscosity of engine oil should not be too high or too low. If the viscosity is too high, it will increase the resistance during engine operation, which can affect the engine's power output and fuel consumption. If the viscosity of the engine oil is too low, it will not be able to form a stable oil film on the surfaces of various engine components during operation, which will exacerbate engine wear.
When I first started driving, I didn't know much about engine oil, but later I learned that the 15w40 diesel oil grade is quite particular. The number 15w refers to the flowability at low temperatures in winter—the smaller the number, the easier it is to start the engine in extreme cold without freezing. The 40 indicates the viscosity at high temperatures—the larger the number, the better it protects internal engine parts from wear during intense operation in hot weather. As a diesel truck driver, I've experienced the struggles of sub-zero temperatures in the north: using the wrong oil makes starting the engine extremely difficult, and it might even refuse to run. Now, I use 15w40, which adapts to seasonal changes and works well in both winter and summer. The key is that diesel engines are different from gasoline engines—their high-pressure fuel injection systems are more delicate, so the oil must withstand high pressure and contaminants. 15w40 is specifically designed for these conditions, protecting engine longevity. Regular oil changes are crucial—I check the oil level and color monthly to ensure smooth engine operation. In short, choosing the right oil saves a lot of money and avoids the hassle of breakdowns on the road.
