Remind me what machine you ride?
nvrmnd, I searched and found it. Old man brain freeze here.
I just filled the tank on my AK 550 last week and have been getting around 54 mpg +/-1 for combined city (35-40 mph) and country highways (45-55 mph). That's my average for the last several tanks of gas. I now have a bit more than 4200 miles on mine.
I think you'll find the best mpg will be at uninterrupted speeds of 40-50 mph on this bike.