THE PILOT WAS WITHIN THREE MILES OF HIS INTENDED DESTINATION WHEN THE AIRPLANE EXPERIENCED A TOTAL LOSS OF ENGINE POWER. THE INVESTIGATION REVEALED THERE WAS NO USABLE FUEL IN EITHER TANK. THE PILOT HAD BASED HIS FUEL CONSUMPTION CALCULATIONS ON THE 32.5 GALLON CAPACITY PLACARDED ON EITHER TANK. THE TANKS WERE ACTUALLY 30.0 GALLON TANKS WITH 27.5 GALLON USABLE CAPACITY.