we just achieved a best ever(25MPG) in my wife's camaro. i say we, because i drove much of the tank while my car was in the shop. my wife drives almost entirely in stop and go traffic, but my hwy driving and light hypermiling helped greatly.
lots of hwy driving @ less than 2k rpms and as much DFCO as possible got it done. wish i could convince her to let me drive it an entire tank. not gonna happen!
bet i could get 30+ if i just drove to work in it.