Do I need to wash the car when I return it ?

Wipe it with clean old clothes inside, and don't worry about the outside. Generally, as long as it doesn't smell or have stains, it's fine.

Not necessary

There should be no food residue.

You don't need to.

Please do not leave any garbage or food residue in the car. You can use the coin-operated vacuum cleaner at the gas station to clean it up, otherwise you may be charged a cleaning fee.