I did battle with my dealership over these exact fuel gauge and tank issues. They were never fully resolved; I had to fight with the dealership and SOA every step of the way, and to this day has never been fully resolved to my satisfaction.
The Subaru uses an unusual saddle shaped fuel tank configuration. This saddle shape allow the rear drive axel to pass just under the fuel tank. Because of the saddle the tank has two sets of sensor on each side of the saddle. I believe that the tank configurations and the way the sensors pick up the fuel level are the cause of most of these type of problems.
The fuel gauge in our '99 Legacy Wagon never reads consistently and rarely shows Full after a fuel fill up. The mileage per tank(~390mi) and the fuel light are the only indicaters we can use to judge when the vehicle needs fuel.
This vehicle also had a tendency to cause the gas station fuel pump to prematurely shut off when refueling. Because of this and the fuel gauge inaccuracies. It made it a problem to fuel the vehicle, because you never knew if it was actually full or not. This problem was partially resolved by replacing the fill tube to the fuel tank, which has a vent mounted to the fill tube.
I understand that fuel gauges in cars are not that accurate, but at least they should be consistent.
The dealership, Nate Wade Subaru:monkey: , SLC, lost my business over this and other issues with the same vehicle, and has made me question buying a Subaru in the future.:monkey: