my modded stock tomos A55 builds (40-45 mph top speed in commute to work through suburbs) would average over 100mpg, yeah, i calculated it by measuring gas used over miles)
My kitted E50 might be half that. its probably better now that the clutch slips less but i also spend alotta time climbing hills.
i use ethanol free gas and synthetic 2-stroke oil because i dont ride that much (ethanol absorbs lots of water into solution) and i run a ratio of about 70:1 mix gas (new fancy oil lets ya do that). Whether or not ethanol free helps MPGs is highly debatable and greatly depends on your situation.