Milage After Tank On E

Returning from a long outback trip still carrying a full jerry can of fuel I reached 'Empty' still 100 Kilometers from home, reached home and later drove another 25 Km before running dry. Even full it never reads more than 7/8 ful though, same from new. It was a hot trip, the air radiator fan and housing melted near White Cliffs, New South Wales!