Used the Downtown, bigger gas tank, seemed like 2.5 to fill up around 180 miles were the usual numbers. I carried a spare 1 gallon can under the seat, used it once for a buddy who ran out. His BMW was getting terrible milage.
The GT presents a real challenge for out of town usage since the gas tank is smaller and the filler is under the seat. First you have to lift the seat which means taking my clothes duffel off, also, will have to strengthen the seat hinge area. Ruminating about connecting an auxiliary gas tank to the real gas tank above the seat. The underseat storage area is small, dont know if I could fit my tools/parts there.