I have noticed that my mileage varies a lot depending on how hard I push it.
The best tank of fuel so far has been right at 73 mpg. On this tank, I rode VERY conservatively, kept the speed under 45 mph the entire time, and only went wide open throttle a couple of times when accelerating.
The worst tank I have seen was 48 mpg. This was cruising on the highway at full throttle the entire time with a suit case strapped to the passenger seat which stuck out in the wind slightly on both sides, and a cooler strapped to the top of the suit case.
I found that when the fuel gauge shows half a tank, that is when 1 gallon of gas has been used. The most fuel I have ever put in the tank was 1.7 gallons, and the fuel gauge was below the E. I typically fill up though when the needle gets into the red and it typically takes 1.2 to 1.4 gallons to fill it up.