How much money does the United States save through greater fuel efficiency?

An article from Newsweek yesterday makes the case amid a flurry of statistics over three pages that the US economy is coming back in a big way. The most interesting statistic is probably the one on page 3 referring to the benefits of fuel efficiency, especially considering that both the US and Canada have agreed on a single goal for greater efficiency which will make it much easier for auto manufacturers to comply instead of having to work with patchwork laws that vary by state and country. The stat on page 3 is as follows:

So one mile per gallon efficiency = 6.1 billion gallons of gas and $17 billion saved per year. Fast forward to 2016 (just six years away) and the extra 15 mpg efficiency will then result in 91.5 billion gallons and $255 billion saved per year. At 42 gallons per barrel that's 2.2 billion fewer barrels being used per year, or 6 million per day. Current oil consumption is 20.8 million barrels a day, so the difference is huge. The difference in geopolitical terms can be seen here where each 1000 represents a million barrels per day.