I wondered why this was only with Ford/GM cars myself - presumably, all of the cars these days are sending the fuel level via CANBUS, so it isn't just the lack of the sensor data from other manufacturers. Purely a guess, but perhaps there _isn't_ a device that National plugs into all of its cars - the overhead to maintain, network fees, etc may not be worth it. Instead, they may be using the existing OnStar hardware with GM's fleet management software https://www.fordpro.com/en-us/intell...eet-management to read the fuel levels.

If so, this is good news - just continue to avoid GM vehicles. I wouldn't mind as much personally, if they gave us verification of the fuel level when you pick up the car, and there was a gallon-or-two 'grace' amount where they charged you at ~market rate, before going to the much higher 'convenience' rate for the rest.