I purchased the 2011 Sonata on Labor Day last fall. I have almost 40K on it with most of it coming through hwy runs between Chicago and Mpls. I get 38 MPG running on at 74 MPH on cruise.

Even in Chicago traffic, I average 28-29 MPG with a normal mix of miles.

 

Readout on mine is reading like 18-19mpg with my commute... i only drive like 2 miles though with like 4-5 stops and a drive up 3 parking garage levels.. dunno seems low but my commute is stop and go and comp may not be accurate

 

My 11 GLS with 17K (in-service date 2/10) gets 27 in town and 39 highway, recently drove it 3400 miles through 7 states, A/C, 70 mph, 2 adults and luggage and averaged 37 mpg. No complaints.