Which consumes more fuel, 5w30 or 5w40?

[McJake]

5w30 and 5w40 are not comparable, as engine oil has a very minimal impact on a car engine's fuel consumption. Moreover, 5w40 and 5w30 are merely specifications of engine oil, which is further categorized into: full synthetic oil, semi-synthetic oil, and mineral oil. The effects vary depending on the oil brand, and using higher-quality oil does not necessarily benefit the engine. Engine oil is a consumable, and different engines require different types of oil. The functions of engine oil are: 1. To separate the surfaces of relatively sliding parts, thereby reducing wear; 2. To carry heat back to the oil tank and then dissipate it into the air, assisting the radiator in cooling the engine; 3. To circulate carbon deposits, sludge, and worn metal particles from engine parts back to the oil tank, flushing away contaminants generated on the working surfaces of parts through the flow of the lubricating oil.