Last tank got 220 miles from about 6 gallons, or about 37 mpg. Should be better. I will be adjusting the valves soon and maybe that will make a difference. 90% of the mileage was on the highway, which helped a lot. It drops quite a bit around town.
Gas gauge was down to 0-1 bars, and the fuel light was on. It is an 8 gallon tank and it took 6 gallons, so conceivably there were 2 gallons left in the tank. BMW says that the light will come on with 1.1 gallons left in the tank. Everyone else says that the tank has two lobes that hang down on either side of the frame and that fuel is only taken from the right side, so that you have extra fuel in the left lobe that you can't get to. (Unless you lean the bike way over to the right.)
I don't yet know how low I can go before I sputter to a stop. I am sure I will find out.