I think my tank is only 5.5 gallons. Is yours 5.9?I rode hard today up and over Sonora Pass, a 10,000 foot elevation change, in 100 degree weather, lots of full throttle acceleration and some sustained 80 MPH 2 lane hwy, and filled up 4.6 gallons with 250 miles on the trip meter. So that means I had 1.3 gallons and could have gone another 60 miles or so. Amazing. I just rolled over 10k miles and I think the mileage is getting better.
This thing doesn't seem to vary much, I can ride it gently or really flog it, either way I get mid 50s MPG.