U.S. gasoline prices jumped the most since 2011 between New Year’s Day and early May this year, a few weeks before the unofficial start of the summer driving season—Memorial Day. But the national average price for regular gas has trended lower since it hit its highest so far this year on May 3. Average U.S. prices of regular gasoline were down this Memorial Day weekend compared to last year’s and were lower than last week and last month, too. AAA expected a record number of Americans to have hit the road by car this weekend—at…