Why is the engine noise louder after maintenance?

[Emmett]

After maintenance, the engine noise becomes louder due to reasons such as incomplete draining of old engine oil, using a different type of oil than before, or overfilling with new oil. An engine is a machine that converts other forms of energy into mechanical energy. It originated in the UK and can refer to either the power generation device or the entire machine including the power unit. Engine types include internal combustion engines, external combustion engines, electric motors, etc. Taking the external combustion engine as an example, it burns fuel outside the engine. Invented by Scottish R. Stirling, it's also called the Stirling engine. This engine converts the heat energy from combustion into kinetic energy. The steam engine improved by Watt is a typical example of an external combustion engine.