The engine oil used in Volkswagen LaVida Marine Edition is 5W-30, and its functions are as follows: Lubrication: there is rapid relative sliding between piston and cylinder, and between spindle and bearing bushing. In order to prevent the parts from wearing too fast, it is necessary to establish an oil film between the two sliding surfaces. A thick enough oil film will separate the surfaces of the relative sliding parts, thus achieving the purpose of reducing wear. Cleanliness: Good engine oil can bring carbides, sludge and worn metal particles on engine parts back to the fuel tank through circulation, and wash away the dirt generated on the working surface of the parts through the flow of lubricating oil. Auxiliary cooling: Because the specific heat value of engine oil is low, it is inside the engine, so it has no cooling effect. However, due to the heat generated by fuel combustion in the engine, when the engine is working, the engine oil can bring the heat back to the oil tank and distribute it to the air body to help the water tank cool the engine. What really plays a cooling role is the water outside the engine casing.