I'm thinking it is something electrical either in the tank or with the read out. Yesterday I filled mine for the first time and the gauge only read 3/4. (When I picked it up at the dealer it was also at 3/4). It took 11.8 gallons and I had 1/4 tank, according to the dash readout. Also I know I got a "full tank" because some gas spilled over and ran down the side of my car:( So I drive about 25 miles on the highway and the gauge creeps up to about 7/8. Park the car at my destination. Start the car to leave, full tank on the gauge now??