A while back, auto writer G.E. Miller ranked the 15 most fuel efficient cars sold in the U.S. He set a price cut-off at $30,000, which excluded General Motors' Volt.
The only two domestic vehicles to make the list came from Ford. Here there are: 

11. Ford Fusion Hybrid (same vehicle as Mercury Milan Hybrid and Lincoln MKZ Hybrid)

Price: $28,240
Highway MPG: 36
City MPG: 41
Annual Fuel Cost: $1,187
Annual CO2 Produced: 4.8 tons  10. Ford Fiesta
Price: $14,390
Highway MPG: 38
City MPG: 29
Annual Fuel Cost: $1,404
Annual CO2 Produced: 5.7 tons