The airplane was cruising at 8,500 feet when the engine experienced a partial loss of power. The pilot switched the fuel selector from the auxiliary tank to the left main fuel tank. During the transition, the engine experienced another loss of power. The pilot was unable to restore the power so he shut down the engine and made a forced landing on a road. During the landing roll, the airplane veered off the right side of the road and struck a post, which resulted in substantial damage to both wings. The pilot stated that there were no mechanical malfunctions with the airplane that would have precluded normal operation and that he exhausted the entire fuel supply in the auxiliary fuel tank. An examination of the wreckage by the responding Federal Aviation Administration inspector revealed that the auxiliary tank did not contain any fuel. The right and left fuel tanks contained 4.5 and 20 gallons respectively. It is likely that the loss of engine power was a result of the brief fuel starvation during the transition from the empty auxiliary tank.