Mine averages 53mpg. that's city and hiway. On trips, it averages 55 and once 60mpg. It's an '09 with fi. The only engine mods are Zard free flow exhaust and custom made air filters. I cut out the cardboard on the OEM and cut to fit a piece of Uni-Foam. That's the stuff motocross racers often use to make their air filters. Everything else is stock. I had problems with some major drive train mods like Dr. Pulley sliders and a different variator. Since then I keep it stock except for the afore-mentioned mods.
Oh once on a trip I got between 45 and 50 on the hiway. I was fully loaded for scooter camping aka s'camping, including cold weather garb and was riding into a steady north wind.