Which has higher viscosity, 0w40 or 5w40?
3 Answers
5w40 has higher viscosity. The number before W represents the minimum temperature it can withstand. The smaller the number, the lower the low-temperature viscosity, the better the low-temperature fluidity, the lower the applicable minimum temperature, and the easier it is to start in cold conditions. The number after W represents the viscosity of the oil at 100°C. The larger the number, the higher the viscosity, allowing it to form a good oil film at high engine temperatures and be suitable for a wider range of temperatures. Below is some relevant information about engine oil: 1. Function of engine oil: Engine oil lubricates and reduces friction, assists in cooling, seals against leaks, prevents rust and corrosion, and provides shock absorption. It is known as the "blood" of a car. Choosing the right oil and changing it regularly can maintain the engine in good condition and extend its lifespan. 2. Choosing engine oil: The best oil is not necessarily the most expensive; rather, it should be selected based on the characteristics of the car's engine and driving habits. Engine oil can be categorized based on winter and summer use. For winter, the primary consideration is the low-temperature viscosity grade, while in summer, due to high temperatures, there is no need to choose oil with a superior low-temperature viscosity grade.
I've been into cars for many years and have used various engine oils. This issue seems quite common. The '40' in both 0w40 and 5w40 is the same, indicating they have the same viscosity at high engine operating temperatures, both being medium-high viscosity and providing similar protection. However, the number before the 'w' represents low-temperature performance: 0w flows better in cold weather with lower viscosity, while 5w has slightly poorer flow and higher viscosity at low temperatures. So during cold starts, 5w40 has higher viscosity than 0w40 because it's less fluid. But in actual driving, the difference is minimal—I recommend using 0w40 in winter to reduce cold-start wear and 5w40 in summer, which is sufficient, while also referring to the vehicle manual's recommendations. Choosing the right oil in regions with large temperature variations extends engine life and makes maintenance easier.
Having driven in the north for years with winter temperatures often below zero, choosing engine oil requires attention to detail. Both 0w40 and 5w40 have a high-temperature viscosity of 40, meaning they share the same thickness when the engine is hot. However, in cold conditions, 5w is slightly thicker due to its higher flow index compared to 0w, indicating a marginally denser consistency at low temperatures. On the other hand, 0w has lower low-temperature viscosity, enabling quicker engine starts. From a viscosity standpoint, 5w40 is slightly thicker in cold weather, but the difference is minimal. Adjust your choice based on the season—I prefer 0w40 for winter to prevent engine stuttering during cold starts, while 5w40 is a cost-effective option for regular use. Differences in fuel consumption or acceleration feel are negligible; the key is timely oil changes for safety.
