I keep my ship waxed! Plexxus that wind shield, stay tucked tight, steady throttle, and I get 38mpg. Ride in the rain, in the cold, in the heat, windshield up/down, top case on/off I get 38MPG. I quit checking. The gauge says filler' up and I do. Repeat.
I consistently got 48-50 on K1200lt riding slab cross country. But in 5th gear at 75 she was only turning around 2500RPMS.
Regarding that instant MPG on the bike computer. I've seen 84mpg before! IT will jump all over. I was having so much fun with it, I nearly killed myself! MUST PAY ATTENTION! That's when I quit looking at MPGs. I now pay attention to GPGs. That's GRINS per Gallon!