This article talks about a professional hyper-miling crew from Australia that drove the Chevy Cruze Eco through all the 48 connected states, and averaged 64.42 MPG!
The Chevy Cruze was completely unmodified, and a new one can be bought for a base sticker price of $19,999. The EPA puts an automatic Cruze Eco at 26 mpg city and 37 mpg highway and a manual at 28 mpg city and 42 mpg highway.
Of course, they're professionals, so our own results would probably only be 42 MPG or something similar
Interestingly enough, the Chevy Volt sales seem to have slowed down (some even say slumped) while the Cruz and Cruz Eco sales are soaring. The Nissan Leaf is also outselling the Chevy Volt.