There are a wide variety of motorcycles out there, with various capabilities. Average mileage is often around 45mpg, and tanks usualy have 3 or 4 useful gallons. A KLR650 has a 6 gallon tank, which is one of the larger stock ones, and there are a multitude of add-on tanks for long-distance riders or racers. I personally look forward to a 150 mile range, it forces me to stop and rest and keep my head fresh. Motorcycle requires complete attention, unlike many cars.