“The Prius is marketed as a fuel efficient car. In the United States, Environmental Protection Agency (EPA) test results must be posted on new vehicle windows in the U.S. and are the only mileage figures that can be advertised. Similar to other vehicles, Consumer Reports viewed the initial estimate as flawed and issued their own assessment giving a real-world mileage of 44 mpg–U.S. (5.35 L/100 km / 52.8 mpg–imp) for the Prius instead of 55 mpg–U.S. (4.28 L/100 km / 66.1 mpg–imp) (51 highway, 60 city). EPA testing procedures for all vehicles were revised in 2007. According to the EPA's revised estimates, the combined mileage for the 2008 Prius is 46 mpg–U.S. (5.11 L/100 km / 55.2 mpg–imp), making it the most efficient car of 2008.

As with all vehicles, these numbers are only estimates for the average driver. Individual situations will vary based on length of commute, average speed while driving, number of hard stops and starts, tire pressure, outside temperature and other factors. Worst case scenario is a short commute (less than 5 miles (8.0 km)), fast acceleration and stops, tires below the minimum recommended pressure of 35 psi front/33 psi rear, and extreme cold conditions.”
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Fey Tuffbar Bumpers