Well, my wife, 70 lbs of gear, and I went 4789 miles door to door from Oceanside, CA to Sturgis, SD and back. We averaged 44.45 miles per gallon of fuel (hot-rodded 103 cid). I put premium from whatever gas station was convenient. All 91 octane except for a Cheyenne, WY station that had 92. What a great trip, we hit eleven states. The ride there and back was some of the best times I have ever had.
Almost forgot:
Oops-did run out of gas three miles short of Gillette, WY (yes, that was me pushing and my wife sitting on the bike navigating.)