Many of the newer vehicles are "connected" to the Avis back-end system. You can tell if your vehicle is connected by looking in the app - if it shows the actual gallons of gas in the vehicle (with a slight delay), the car is feeding back information to the system, including gas level, mileage and location. If the agent scans the barcode on the vehicle, they can immediately have the fuel level and mileage on their device. This eliminates the need for them to look at what the gauges say. The only issue that I've found with this is that sometimes if you fill-up near the airport, it doesn't always sync immediately and they register you as bringing in a non-full vehicle. Then it becomes the usual fight to get the charge reversed.