The pilot was engaged in sheep spotting. The aircraft had been refuelled two days prior to the flight and before DEPARTURE the pilot had checked the fuel contents gauges, which indicated full fuel. After about two hours of the planned three hour flight, the pilot noticed that one the fuel contents gauges indicated empty and the other almost full. As he was near one of the property airstrips, the pilot decided to land the aircraft and dip the tanks. Having apparently satisfied himself that sufficient fuel remained he continued the flight. An hour later, as he was returning to the Station airstrip, the engine stopped. The aircraft was landed on a road but during the landing roll the left wing struck a tree and the aicraft ran off the road and into the bush, sustaining further damage. An inspection of the aircraft revealed that the engine had stopped after the usable fuel had been exhausted. The fuel gauge for the right fuel tank was found to overread by 10 litres, however the reason the fuel had been exhausted after a flight time of only three hours could not be positively determined.