Justo for info., on my WR450 with FMF powercore 4 with silent insert, I got 62 miles to the gallon. (125 miles on 1.96 gallons) This was on 50% easy road/trail going around 7000 to 9000 feet. There were some hard climbs but mostly not very challenging. The jetting is stock but I turned my fuel screw to one turn to lean it at that altitude. I checked the specs and the 2.2 gallon tank has only .3 gallon reserve. So under the best of conditions, you have probably 18 miles left on reserve.