Well, I've put 8K miles on my Berky since Memorial Day. From Phoenix to Denver, out to Elkhart and then up to Glacier NP. Then on to Seattle and from there south to San Francisco. Finally out to Elko, NV and the down to Las Vegas which is probably going to be my "wintering location"
In this rather extended trip, I've averaged just over 11 MPG. I've seen it as high as 12.5 and as low as 9.5 but overall I'm right at 11 to 11.2. At one point I actually saw 13.2 but think I may have had a pretty good tail wind, so I'm not counting that segment.
Yesterday, coming from Elko, NV to Las Vegas, NV (440 miles) I averaged 12.1
All in all, pretty good for a "big old coach".