Can 5w40 and 5w30 be mixed?

[ODaniella]

5w40 and 5w30 cannot be mixed. The judgment methods for when engine oil needs to be changed and the precautions for use are as follows: Judgment methods for when engine oil needs to be changed: The simplest way to check the shelf life of car engine oil is to observe whether the viscosity of the oil has changed, determine whether the smell of the oil has faded, and observe whether the color of the oil has changed. When observing changes in oil color, pay attention to changes in additives within the oil. Additionally, filter paper or electronic instruments can be used to check whether the shelf life of car engine oil has expired. Precautions for using engine oil: The selection of engine oil should be based on the requirements of the engine. Choose oil that matches the engine. Oils of different brands cannot be mixed. Multi-grade oil should be selected as it has advantages such as savings, long service life, and high efficiency, providing better protection for the engine. The oil level should be slightly below the mark on the dipstick and not overfilled.