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. You will find a fuel car in the glove box, use this to pay for the fuel. You do not need to keep the receipt.
You must refuel with the lowest cost fuel available suitable for that vehicle. Each car has a user manual located in the glove box with fuelling instructions for that particular vehicle.
Refuelling when your car is below 1/4 full is one of the important rules that makes car share work. If you don't do this, and the next member is inconvenienced, you might get fined.