Incident Summary
After approximately 3 hours and 20 minutes of flight, the pilot encountered a complete loss of engine power. He attempted to reach the nearest airport but was unable to do so, ultimately performing a forced landing in a field located 3 miles from the airport. No mechanical problems with the aircraft were reported.
Fuel Management
Before departure, the pilot estimated that the aircraft carried enough fuel for 4 hours of flight. However, the airplane's usable fuel capacity was 33.5 gallons, and the fuel consumption rate was about 9 gallons per hour. Under these conditions, the total endurance, assuming proper leaning, would be approximately 3.7 hours, not accounting for fuel used during takeoff, taxi, and climb. The aircraft had been serviced with automotive fuel.
Findings
The investigation determined that the power failure occurred due to fuel exhaustion. The pilot's estimate of 4 hours of fuel was not consistent with the calculated endurance based on the fuel load and consumption rate.