Your rental car will be provided to you with a full tank of fuel, and this is how you are expected to return it. You will need to find a gas station close to your rental depot, to make sure you return it with a completely full tank and avoid any additional charges. Customers who have not made any prior arrangements, and do not return the car with a full tank, with be charged an additional fee. You will be charged at a rate for the fuel that is generally higher than the local gas stations.
If you want to avoid searching for a gas station, you can choose to pre-purchase the full tank of gas directly from the car rental company. You will be charged at a competitive rate, similar to the cost of other local gas stations. Generally, you are able to purchase the full tank only, so this may not be your preferred option if you are only planning to travel a short distance.
Read more about returning your rental car.