You don't need to refuel with every booking.
If the fuel gauge dips below 1/4, then you need to refuel. Please stop and fill up all the way before you return your car at the end of your booking.
Refuelling when your car is below 1/4 full is one of the important rules that makes carshare work. If you don't do this, and the next member is inconvenienced, you might get fined.