You may be doing a double take the next time you fill up your gas tank.  According to Iowa Triple-A, the statewide average price of a gallon of regular unleaded gasoline is $1.64.  That’s down 11 cents from last week, and down one dollar from one year ago.  And the statewide average for a gallon of diesel is $2.28—down six cents from last week and 68 cents less than it was one year ago.