THE COMMERCIAL PLT HAD FLOWN 3 HRS & WAS STARTING THE LAST LEG OF A PART 135 PASSENGER FLT. HE SAID HE DID NOT FEEL COMFORTABLE WITH THE FUEL GAUGE READINGS. HE DISCUSSED THE PROBLEM WITH THE CHIEF PLT/OPERATOR & WAS TOLD TO PROCEED TO MOAB. THE PLT SAID THE CHIEF PLT DID NOT LOOK AT THE GAUGES. HE WAS ALSO TOLD THAT THE FLAPS ON THIS ACFT DID NOT RETRACT COMPLETELY. THE PLT SAID THAT AFTER 30 MIN OF FLT, THE ENG LOST POWER. A PASSENGER THAT WAS ABOARD THE ACFT SAID SHE HEARD THE PLT RADIO THAT THE ACFT WAS OUT OF FUEL & THAT HE WAS MAKING A FORCED LANDING. THE PLT SELECTED A DIRT ROAD IN ROUGH TERRAIN (APRX 5 MI SW OF THE DESTN). DRG THE LANDING ROLL, THE LANDING GEAR COLLAPSED & THE RGT WING STRUCK A TREE. ANOTHER COMPANY PLT FLEW OVER THE DOWNED ACFT & COORDINATED RESCUE EFFORTS. BEFORE THE PLANE WAS RECOVERED, 6.1 GAL OF FUEL WAS DRAINED FROM THE FUEL TANKS. THE ACFT FLT MANUAL STATED THAT EACH OF THE 2 TANKS CONTAINED 3 GAL OF UNUSABLE FUEL.