My last trip two weeks ago from PA to NC, I managed 32mpg, about 450 miles on 14 gallons. I actually put 14.1 gallons in the tank. The 'Tour has a 15 gallon tank, but they say there's a reserve amount of fuel in the tank. I have;
2000 SE V6 MTX
I used Sheetz gasoline
I drove ~78mph on cruise south on rt's 81 and 77
