Description: We already knew the 2010 Toyota Prius would put up some impressive fuel economy numbers but the official Japanese numbers are just insane. On the standard 10-15 test cy... view allDescription: We already knew the 2010 Toyota Prius would put up some impressive fuel economy numbers but the official Japanese numbers are just insane. On the standard 10-15 test cycle, the new Prius is rated at 89.4 mpg U.S. with CO2 emissions of just 61 g/km! While the new Prius is certainly efficient, these numbers certainly seem highly unrealistic. view less