The pilot reported that after descending from 8,000 ft above mean sea level (msl) to 5,000 ft msl following a 2 hour cross-country flight, the engine power decreased from 2,300 rpm to 1,500 rpm. The pilot attempted to troubleshoot the partial loss of power by applying full rich mixture, ensuring that both fuel selectors were selected to the main wing tanks, and he turned on the electric fuel pump; however, full power was not restored. The pilot advised air traffic control of the emergency and he was informed of a nearby airport that required a 180° turn. While maneuvering to the airport, the engine lost all power, the descent rate increased, and the airplane impacted terrain and trees as the pilot attempted to land on a small road. The wings and fuselage sustained substantial damage.Examination of the airplane at the accident site discovered that no fuel was present in either main wing tanks, nor was there any evidence that fuel had leaked from either main tanks. The left tip tank contained about 3 gallons of fuel, and the right tip tank was found empty, as it had been breached during the collision with trees. Examination of the engine revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. Furthermore, the main fuel tank fuel lines and engine driven fuel pump displayed no evidence of fuel present when examined. There was also no evidence of in-flight fuel siphoning leakage discovered on the fuselage or wings.The pilot reported that about 59 gallons of fuel was onboard for takeoff. It was estimated that for the 2 hour and 15 minute flight that had elapsed the airplane likely consumed about 31 gallons of fuel. He reported that during the preflight inspection he checked the fuel quantity visually, and he recalled that the main tanks were about his finger length from full. Page 2 of 7 ERA22LA291The pilot reported that he did not top-off the fuel tanks before departing, and that throughout the flight he switched between the left and right main fuel tanks, feeding the engine from one main tank at a time. He did not use the tip tanks during the flight. During the descent, he switched both main tanks to the on position. It is likely that the pilot’s initial partial loss of power was due to one of the main tanks containing no fuel, which introduced air into the fuel lines. The flight manual supplemental cautioned pilots from selecting a tank that contains no fuel. A few minutes later, the remaining wing tank likely was exhausted of fuel, which resulted in the total loss of power. The investigation could not determine the discrepancy between how much fuel the pilot reported that he departed with versus what was likely consumed, and ultimately discovered on board at the accident site. The pilot had added fuel multiple times in the days preceding the accident between flights; however, the pilot did not use the fuel calculator onboard the aircraft and the fuel gauges postaccident indicated that both main tanks were about 1/4 full, when in fact they were both empty. These factors contributed to why the pilot likely departed with less fuel than he realized.The pilot could have used the tip tank fuel while en route; however, the tip tanks were only to be used during level flight; thus, after the partial loss of power, the tip tanks were likely not a reliable source of fuel for the engine given the maneuvering that would have been required to reach the alternate airport. Had the pilot departed with sufficient fuel and topped-off the tanks before departure, or managed the fuel appropriately en route, the fuel starvation would have been prevented.