I have an 06 LBZ CC SB, and have been seeing anywhere from 14mpg (all streets mostly), to about 18 on the highway.

I've not been on any long trips (+50miles ea way) to test out to see if I can get 20mpg on the highway (at 67mph).

I've been making a table of a bunch of information so that when I hit the magic break-in number I can see the fuel economy change.

Thus far, almost 3400 miles in, i'm still seeing about 15.