After reading this thread, I tried my best to reach 50mpg, but failed
This weekend I rode two-up for 600 miles (300 to reach the seaside + 300 back home)
On Friday evening I kept the cruise control stuck to 75mph for almost 3 hours and a half (GPS measured... about 80mph on the speedo) and reached 47mpg (measured when refilling after 280 miles). BC was telling 1-2% more on mileage (I reset the BC when I refill).
No traffic, all on a flat, straight freeway with no stops except the one to have dinner and gas. Temperature 100F, V-Stream windscreen about 80% down, winglets 30% open.
I believe that's amongst the highest mileage I've ever seen (measured on refill): I've occasionally seen >50mpg on the BC when riding on country roads at 55-65mph but I've never rode a full tank at that speed to perform an accurate measure. Other times I've seen 46-47mpg at refill, so I think that's about my best
On the way back, I've set the cruise control to 81mph (legal speed in Italy, GPS measured) and had also a flawless ride (no traffic, no stop-n-go), but scored only 40-41mpg. It's amazing how much mileage difference I got, for just +6mph.