What is the difference between 5w-40 and 5w-30?

[JoannaDella]

5w-40 and 5w-30 mainly have the following differences: 1. Different high-temperature viscosity: 5w40 has higher high-temperature viscosity, poorer fluidity, but smaller fluctuations and greater stability; 5w30 has lower high-temperature viscosity, better fluidity, and faster engine heat dissipation. 2. Different applicable objects: 5w40 has higher viscosity and is more suitable for older cars; 5w30 can effectively reduce fuel consumption and has lower noise, making it suitable for new cars or naturally aspirated engines. These two types of engine oil are called all-season universal gasoline, not only having fluidity for low-temperature starts but also a relatively thick oil film under high-temperature conditions, so these two types of engine oil are suitable for all seasons.