I kept track of my gas purchases from Ocala Fl to Alaska and back to Big Spring Tx. After my mishap in Tx I gave up but thought some of you maybe interested in what I found. Highest MPG was 51.6 on interstate leaving Fl and Ga (ridden this part of country many times so just trying to put it behind me). I ride around 70-80 on the interstate but go as high as 90. I got 50.2 MPG the first tank after I left Roswell NM also. Two lane flat straight rode with some towns.
Worst MPG was 36.8 coming over the mountains headed into Skagway Alaska, it was 35 degrees and I saw snow flakes, Very twisty and huge elevation changes. I must say it was one of the most enjoyable parts of the ride. The other thing was the last place I got gas before heading up had only 87 octane. I waited until the last stop to ensure I had enough gas to complete and was dismayed when I found they only had 87. I must say this happened three times on the Alaskan highway and two were on consecutive fill ups. The bike preformed the same with 87 and the MPG was only much lower on this tank not the other two. I also pulled into a station on 60 east in the mountains coming out of AZ going into NM (great ride) and the station only had 86 octane so I filled her up, again saw no difference in performance including pinging.
I did not carry gas and never came close to needing it. I did have a low fuel light warning a couple of times, but it was when I was heading into a metro area where I was not worried about gas or I could have stopped earlier. I also did not ride to the Arctic Circle, really was not interested in it, but the weather (rained everyday I was in Alaska) made up my mind about not riding it.
Both side bags filled to capacity, a large sears top case filled to capacity, and a equipment bag with a sleeping bag, two man tent, single air mattress, air pump, and air plane pillow on the back seat. A small tank bag type bag on top of that with maps, chargers rain gear etc. She was pretty loaded down.
The overall MPG for the trip that I kept track of (about 3/4 of the overall trip) was 43.8, not bad considering the load and how hard I pushed her in the mountains and on the twisties. I experienced octane levels from 86 to 94 and they did not seem to have much of an effect on MPG.