I am coming up on 10,000 miles soon and so far I have a worst tank of 17.2 and a best of 22.5
The best was a trip up north on the highway and rural NH back roads which average 45-50 mph. I seem to average 17-19 depending on how much highway I get on my daily travels. I have not had a complete tank of just highway miles to see what it could do but I bet it would be better.
I ran it on the dyno to see where it stands, Janety Racing, with a 216.6rwhp and a 393.1rwtq.