On September 20, 2004, about 1500 Pacific daylight time, an experimental IAR SA Brasov 823, N823WT, experienced a loss of engine power and collided with terrain during a forced landing near Denair, California. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The commercial pilot and one passenger were not injured; the airplane sustained substantial damage. The personal cross-country flight departed Reno/Stead Airport, Reno, Nevada, about 1330, with a planned destination of Turlock Municipal Airport, Turlock, California. Visual meteorological conditions prevailed, and a flight plan had not been filed. In a written statement, the pilot reported that he had flown to Reno several days prior to the accident, and during the duration of his stay, he parked the airplane in a tie down area on the ramp. Prior to departing, the pilot performed a preflight inspection, at which time he visually verified the airplane's fuel quantities by both physically looking inside the wing tanks, and by checking his fuel computer/totalizer inside the cockpit. The pilot did not use a dipstick or other means to physically verify the quantity. He estimated about 33 gallons of fuel on board, which he thought would be more than adequate for the 1- to 1 1/2-hour flight. Having flown the same route of flight many times before, he calculated the airplane's fuel burn to be about 13.4 gallons per hour. The pilot stated that while en route, he compared the "fuel remaining time" with the "time en route remaining" on his gauges numerous times. As he came in the proximity of Turlock, about 3 miles away, he maneuvered the airplane in a descent to 1,000 feet above ground level in preparation to enter the left downwind leg of the traffic pattern for runway 30. The engine coughed once and subsequently quit. In an effort to troubleshoot the engine's loss of power, he turned the boost pump to the "on" position, manipulated the mixture knob to the "full rich" position, and verified the fuel selector was in the "both" position. Despite his efforts, the engine would not restart and the pilot configured the airplane for an emergency landing; he opted to land between sprinkler systems in alfalfa field. While descending, the left wing tip contacted the ground first, and the landing gear touched down on the soft wet ground. The pilot further noted that after egressing the airplane, he tried to troubleshoot the engine failure. He discovered that the left wing tank was empty, and the right tank had a very minimal amount of fuel left inside. The fuel computer/totalizer indicated 13.1 gallons remaining. The airplane incurred damage to wings, landing gear, and propeller. After recovery, under the auspice of a Federal Aviation Administration inspector, the pilot drained both fuel tanks and found about 1 gallon of fuel remaining. The pilot opined that 12 gallons of fuel was siphoned from the airplane while on parked on the ramp at Reno. He stated that this missing amount of fuel would not be detected by the fuel calculator/ totalizer, and would be difficult to assess when visually inspecting the fuel tanks (about an inch difference). He further noted that the accident could have been prevented if he had used a quantity dipstick. The pilot reported no mechanical malfunctions of failures with the airplane prior to impact.