On May 18, 1995, about 1054 eastern daylight time, a Cessna 172G, N3722L, registered to HRN Wings Inc., leased to Aviation Training Associates, operating as a 14 CFR Part 91 personal flight, experienced a reported loss of engine power in cruise flight. The airplane crashed during a forced landing to an open field about 3 miles east of Central Florida Regional Airport, Sanford, Florida. Visual meteorological conditions prevailed and no flight plan was filed. The airplane sustained substantial damage. The commercial pilot was not injured. The flight originated from Boca Raton, Florida, about 1 hour 24 minutes before the accident. The pilot stated he made a power on descent from 4,500 feet agl to 2,500 feet agl without using carburetor heat. He started to descend to 1,000 feet agl, and the engine started running rough. The carburetor heat was turned on, and the fuel selector valve was moved to the right fuel tank. The engine quit, and the fuel selector valve was moved back to the left fuel tank, and an engine restart was attempted with negative results. The fuel selector valve was moved to the both position, and an engine restart was attempted with negative results. A forced landing was made to an open area. The airplane stalled, and collided with the terrain. The President of Aviation Training Associates Inc., stated the airplane was refueled on May 17, 1995, and had 31 gallons of fuel on board at takeoff. The airplane was dispatched with a starting tachometer reading of 20.49, and a Hobbs meter reading of 130.10. The tachometer reading at the crash site was 24.17, and the Hobbs meter reading was 133.7. This equates to 3.68 hours of tachometer flight time, and 3.6 hours of Hobbs flight time. Review of N3722L refueling records over a 6 month period of time indicates N3722L average fuel burn rate is 9.1 gallons of fuel per hour. Examination of the fuel system by recovery personnel revealed 1 gallon or less of fuel was present in the left and right fuel tank. Examination of the engine assembly and accessories was conducted by the FAA on May 18, 1995. No fuel was present in the gascolator. The Information Manual for the Cessna 172, Section 2, Description and Operating Details, states usable fuel all flight conditions is 18 gallons. The total volume of fuel in each fuel tank is 19.5 gallons.