When you car is new, you take it for a ride till you are tired. During those trips, the car will be exposed to lots of elements and in time, the dust and other filthy things will accumulate. That is why; you will need to clean it at some point. But, if you are too busy to clean your car then just go to the car wash and have it clean.
The game is played via mouse and you need to interact with the surroundings to play the game. Of course, you would need to wash the car, put some soap, wash it again. Dry it with a piece of cloth and wax it. That is pretty much that you need to do in this game.