THE PILOT FAILED TO VISUALLY INSPECT THE FUEL LEVEL BEFORE DEPARTING ON THE ACCIDENT FLIGHT. DURING THE FLIGHT, THE LEFT FUEL GAUGE FLUCTUATED BETWEEN FULL AND EMPTY WITH THE RIGHT FUEL GAUGE INDICATING 1/4 FULL. THE ENGINE LOST POWER DUE TO FUEL EXHAUSTION WHILE ON FINAL APPROACH. DURING THE FORCED LANDING THE AIRPLANE COLLIDED WITH A TREE AND CAME TO REST ON A HIGHWAY 300 FEET SHORT OF THE RUNWAY. POST CRASH EXAMINATION FOUND LITTLE OR NO FUEL REMAINING IN THE INTACT FUEL SYSTEM.