The fuel policy is determined by the car rental supplier and vary between different options and locations. Here is an overview of the most common fuel policies:
Full to full:
You'll receive the car with a full tank of fuel and leave a deposit. As long as you return the car with a full tank of fuel, you'll get the deposit back. If you don't return the car full, you'll be charged for missing fuel and a refuelling fee.
Same to same:
Your vehicle will be supplied with fuel and you need to return the car with the same amount of fuel. You may be required to leave a fuel deposit reserved on your credit card that will be released when you return your car with the required amount of fuel. Missing fuel will be charged on your return.
Pre-Purchase with partial refund:
Your car will be provided with a full tank of fuel for which you will need to leave a deposit at the rental counter. Upon return of the car you will be refunded for the unused fuel, but you will be charged a mandatory admin fee. The admin fee is non-refundable regardless of the amount of fuel upon return.
You pay for a full tank of fuel when you pick up the car, and you can return the car empty. However, you are usually not refunded for fuel you don't use and the fuel is usually charged at a higher than normal rate.