Which is better, 5w30 or 10w40?

[LaWalter]

There is no direct comparison between 10w40 and 5w30 because different types of engine oil are designed for specific engine operating conditions. The key is to choose the appropriate oil for your vehicle. Below is an introduction to engine oil knowledge: 1. Engine oil selection criteria: If the manual recommends using 5w30 oil, using a higher viscosity oil like 10w40 by mistake will reduce the oil's fluidity, negatively impacting both fuel consumption and engine performance. However, for older vehicles, using higher viscosity 10w40 oil may actually improve performance (due to better oil film strength), so the choice should be based on the engine's operating conditions. 2. Temperature suitability: 10w40 oil is suitable for temperatures above -25°C and is ideal for regions like North China, Central China, and Southwest China, while 5w30 oil is suitable for temperatures down to -30°C, making it ideal for Northeast and Northwest regions.