On March 2, 2000, approximately 1100 mountain standard time, a Cessna P210N, N6489W, registered to Flight Lease, Inc., was substantially damaged during a forced landing 1 mile north of Gillette, Wyoming. The private pilot and his passenger were not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the personal flight being conducted under Title 14 CFR Part 91. The flight originated in Pontiac, Michigan, approximately 0600 eastern standard time. The following is based on a telephone interview with the pilot and the written accident report he submitted. On the evening and morning before departure, the pilot instructed airport line personnel to service the airplane to capacity (123 gallons). He cautioned the attendants to make sure the airplane was parked on a level surface when it was serviced because "[fuel] will siphon. . .from one tank to another and then overboard." According to the fuel invoice, 95 gallons were added to the fuel load. He checked the weather and determined visual meteorological conditions would exist along the route. He elected to fly VFR at 16,500 feet. He did not file a flight plan. The pilot said he "attained a TAS (true airspeed) of approximately 185 knots" that yielded an average GPS (Global Positioning System) ground speed of 180 knots. For the 1,026 nm flight, he calculated it would 5.7 hours. He was satisfied with these figures because at fuel consumption rates of 15.6 and 16.5 gph (gallons per hour), the endurance is 7.7 and 7.3 hours, respectively. With a 20 minute allowance to climb to 16,500 feet at 24.5 gph, he calculated he would have "over an hour left for reserve after reaching Sheridan." When the airplane was 1 hour out from Sheridan, Wyoming, the fuel gauges "looked suspiciously low" (the Hoskins fuel calculator indicated 27 gallons of fuel remained). At that point, Sheridan was 20 minutes flying time away and Gillette was 22 nm away. He decided to divert to Gillette. Approximately 5 miles north of the Gillette Airport, the engine lost power. He declared an emergency with the Gillette control tower. Due to congestion on the frequency with emergency equipment, the pilot was unable to tell the tower where he intended to make a forced landing. The airplane touched down hard on a flat spot in hilly terrain. The nose landing gear was sheared off and the airplane nosed over. After evacuating the airplane, the pilot returned and checked the Hoskins fuel computer. It indicated 14 gallons. The pilot wrote, "I think there may have been a problem with the fuel computer; that my fuel burn was higher than indicated and thus the unexpected fuel starvation. "I honestly don't know what happened to my fuel. All indications were that I left with full tanks, including A SLIGHT DRIP (emphasis added) from the tanks where it was parked." Burning 120 gallons in 5.7 hours would require a consumption rate of slightly more than 21 gph.