According to the pilot, he was in cruise flight when the engine lost full power. The pilot reported that he did not have enough time to attempt a restart of the engine or to switch fuel tanks, due to the low altitude of the airplane. He elected to conduct an off-field emergency landing. During the landing, the airplane impacted a tree, which resulted in substantial damage to the left outboard wing, right horizontal stabilizer and fuselage. Examination of the airplane by a Federal Aviation Administration inspector revealed the fuel selector was positioned on the right fuel tank- AUX position. The right fuel tank-AUX fuel tank was checked, and no fuel was discovered in the tank, however, about 75 gallons of fuel was drained from the remaining tanks. In a telephone interview with the pilot, he stated that took off on the right AUX tank. The post-accident examination did not reveal any mechanical malfunctions or anomalies that would have precluded normal operation.