The pilot had been engaged in sheep spotting and was returning to refuel when the engine lost power about 2km from the airstrip at a height of 500 feet. The aircraft was landed on a gravel road, but directional control was lost in the loose gravel and the wings contacted some low scrub. When the nosewheel was lowered to the ground, the aircraft veered to the left, and came to rest on the propeller spinner, the nosewheel, and the right wingtip. The fuel tanks were subsequently drained on site and yielded approximately 45 litres of fuel from the right tank. The fuel had drained from the left tank to the right tank because of the aircraft's attitude. The pilot said he had been airborne for 3.5 hours and using the consumption rate of 45 litres per hour, had calculated that he should have had 48 litres of fuel remaining when the engine lost power. However he had not flown a Cessna 182A before, had not read the flight manual, and was unaware of the unuseable fuel quantity. He had been flying a later model which had less unuseable fuel. The flight manual shows that the unuseable fuel quantity is 37.7 litres, and useable fuel quantity is 208 litres. The pilot stated that the fuel selector was selected to both tanks (left and right) for the duration of the flight. During the flight the aircraft was turned frequently and the direction of turn was predominantly to the left. This may have caused fuel to drain from the right wing to the left, and allowed air into the system when the quantity fell below the lowest useable level.