Pennsylvania motorists are paying a little less as they top off the tank this week. As reported by Triple-A, the average price for a gallon of regular fell last week in the Keystone State to just over three-dollars-60 cents. The national average dropped slightly to three forty-five a gallon. Meanwhile, the cheapest gas continues to be found in Mississippi, where the average fell slightly on Friday to two-dollars-96 cents. At the opposite extreme, costs were highest in Hawaii at four-68 a gallon.