Each car rental company has its own fuel policy, which is displayed during the booking process. Your fuel policy will be displayed on your confirmation voucher and on the rental agreement at the car hire counter. If you are renting for 3 days or less, you should highlight this to the car rental company at the time of renting in case they can work out an alternative fuel plan for you.
Most of the car rental companies require a deposit or payment at the start of the rental to cover fuel. The deposit will be refunded upon returning the car, provided that the car is returned in accordance with the policy.