On November 18, 1998, at 2030 hours Pacific standard time, a Cessna 152, N48201, collided with a tree during a forced landing following a loss of engine power near Orinda, California. The airplane was destroyed. The private pilot, the sole occupant, suffered serious injuries. The flight, conducted under the provisions of 14 CFR Part 91, originated at the Corning, California, airport at 1900, and was en route to the Hayward Airport. Night visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that he had been leading another aircraft as a flight of two. The second aircraft, a Cessna 172, was having electrical problems, and all contact between the two aircraft was lost. The pilot of the accident aircraft reported that he leveled off at 2,000 feet agl and configured the airplane for cruise flight with the throttle set at 2,000 rpm. After "two to three minutes" the rpm decreased to between 500 and 800 rpm. The pilot didn't notice any engine vibration, but reported that it sounded as if "someone suddenly stuffed cotton in your ears." He stated that the engine never "coughed or sputtered." Approximately 2 minutes later, the engine lost power completely. He reported that he attempted to restart the engine and transmitted a "MAYDAY." The pilot stated that the squelch on his intercom was not working, causing his microphone not to work. Another pilot overheard and transmitted his calls to Oakland Approach. A Federal Aviation Administration (FAA) inspector from the Oakland Flight Standards District Office responded to the accident site. She reported that she drained fuel from the gascolator and tank sumps and found the fuel to be contaminated with water at a ratio of approximately 35 percent water to 65 percent fuel. She stated that draining the gascolator also yielded grass and other debris. The carburetor bowl contained 50 milliliters of water, 2 milliliters of fuel, and 10 milliliters of an unidentified green fungus-like substance. The fuel dispensing logs at Corning Airport were reviewed and indicated that the pilot received 17.1 gallons of fuel before takeoff. The fuel truck was quarantined immediately following the accident. The fuel was sumped and was found to be within the required specifications. The inspector reported that the aircraft had been tied down on the ramp at Corning Airport for about 3 weeks before the accident. The owner of an airport paint shop had been a prospective buyer for the aircraft and had been inspecting it, but had not flown it during the 3-week period. A prebuy inspection had been conducted on September 9, 1998, at Corning Airport, during which 57 discrepancies were noted by the examining Airframe and Powerplant mechanic, who is also the holder of an inspection authorization. A copy of that list is included in this file. During a postcrash examination of the aircraft, the inspector noted that the right fuel tank cap gasket did not seal. She further reported that neither cap gasket appeared visibly deteriorated. She noted no rust or sediment inside either fuel tank. After adding 1 gallon of Avgas downstream of the firewall fuel filter, the inspector ran the engine for less than 1 minute. She noted no abnormal sounds or discrepancies with the engine or engine gauges. Visual and distillation tests were conducted with the fuel samples at Saybolt, Inc., Laboratories in Martinez, California, in the presence of two FAA inspectors. The laboratory personnel indicated that the contamination was most likely a Naptha-based substance, which is a common gasoline additive for cleaning injectors and is also found in paint. Visual analysis confirmed algae-based contamination from the carburetor bowl sample, and significant particulant contamination of all three samples, including sand and dirt-based matter. A copy of the laboratory report is appended to this file. In a recorded interview, the pilot reported to the FAA inspector that he didn't remember if he had drained fuel from the tank sumps or gascolator during the preflight. He stated that after performing a preflight and "under assurance from those in attendance that the plane was in good shape," he was given instruction in how to use the aircraft radio, which was missing its "tens" digit. The pilot reported that he had conducted a carburetor heat check during his run-up, but had not "gotten much out of it." He further stated that he had planned to rent the accident aircraft on October 5, 1998, but had decided not to fly it because he "just had a bad feeling about it."