Most and Least Efficient Car (ranked by city mpg)

In 2009, judged by city mile per gallon efficiency, the Toyota Prius was elected the most fuel efficient car on the market. MPG city 48 MPG Hwy 45

The least efficient vehicle in the midsize category is the Ferrari 612 Scaglietti, 12 cyl, 5.7 L, Auto(6). MPG city 9 MPG Hwy 16

The Toyota Prius also won as an overall fuel efficient car, only losing by MPG for small two seaters such as the Smart Fortwo.

http://www.fueleconomy.gov/feg/best/bestworstnf.shtml