By now you’ve probably hard the news that the third-generation Toyota Prius, better known as the 2010 Toyota Prius, will be the most fuel-efficient vehicle you can buy in the United States when it hits the market this June. How fuel efficient? Well, with a combined (city/highway) EPA estimated fuel economy rating of 50 miles per gallon, the 2010 Prius is well ahead of the ever-growing hybrid car competition at this point. There simply aren’t any other hybrid cars available that have reached the 50 mpg threshold…not yet, anyway.

However, being on top in the hybrid car segment isn’t exactly new to Toyota. In fact, according to fueleconomy.gov, the 2009 Toyota Prius is listed as the current model year’s most efficient EPA certified vehicle achieving 48 mpg in the city, 45 miles per gallon on the highway for a combined mileage average of 46 miles per gallon. So, how did Toyota further refine this already fuel-efficient sedan?