The GT is now in Iowa. I changed rear end, trans, and engine oil to Royal Purple 75/90, Synchromax, and 10/30. I got 29.9 MPG from Tucomcari, New Mexico to Wichita, Kansas doing 75-80 between towns doing 30! Averaged better than 25 MPG for the 2000 mile trip. I'm impressed.
On my Florida trip I averaged about 25mpg to. I set the cruise on 73-75 and only stopped to pee and get gas.