On October 20, 1999 at 1819 hours mountain standard time, a Cessna 172N, N738FY, collided with a tree following a forced landing near Deer Valley, Arizona. The airplane, operated by Westwind Aviation, sustained substantial damage. The private pilot and his passenger were not injured. The personal flight was operated under 14 CFR Part 91. The pilot did not file a flight plan for the flight. The airplane departed Deer Valley at 1530 on a round-robin flight to Flagstaff, Arizona, and returning to Deer Valley. Visual meteorological conditions prevailed at the time of the accident. The pilot said he did a preflight and checked the left wing tank by sticking his little finger in to see if it came out wet, it did, and at this time he believed he had full fuel tanks. He did not check the right fuel tank. After completing his outside preflight, he started the engine and looked at the gauges. He said the left wing gauge indicated "full" and the right wing indicated "3/4 full." The pilot departed Deer Valley airport and began a climb to 7,000 feet. He said they passed by Sedona and climbed to 9,000 feet and headed north towards Flagstaff. He then climbed to 12,500 feet and flew around Mt. Humphrey's before he started back toward Phoenix. He said he flew to the Phoenix Gateway airport to wait for the sun to set, and did a touch-and-go, and then climbed to 4,000 feet. At this point, he noticed that both float gauges had "stopped bouncing." He said that the bouncing fuel gauges indicated that there is "something in the tank," and a lack of movement may be an indicator of a low fuel state. He said that he felt his options at this point were to proceed to Falcon Field or to head back to Deer Valley airport. He said he felt the gauges had to be wrong. The pilot was northeast of Scottsdale when the engine began to sputter. He dialed in 7700 on his transponder and the engine began to run again. He said he had just crossed Scottsdale road when the engine quit a second time. He stated in his written report that he should have landed at Scottsdale airport, but that there were many houses, and it was the end of rush hour. He elected to continue towards Deer Valley airport. Maricopa Sheriff's officers, who were in the area in their helicopter, said they overheard the pilot tell Air Traffic Control that "he had found some fuel somewhere" as he got the engine started a second time. The sheriff's pilot stated the pilot told the Deer Valley control tower that he ran out of fuel and had to make an off-airport forced landing. The sheriff's officers in the helicopter were asked to assist the airplane in finding a safe place to land and lit up the area for the pilot while he landed on the roadway, approximately 3 1/2 miles northeast of the airport. The airplane struck a small tree during the off-airport forced landing. According to the operator's records, the airplane had been fueled on the day before the accident, with a total of 21.0 gallons of fuel. Another renter flew it for 1.3 hours and did not refuel the airplane. The Hobbs meter readings show the accident pilot then flew the airplane for 3.1 hours.