On January 15, 1995, at 1330 Alaska standard time, a wheel equipped Cessna 172 airplane, N6867X, registered to and operated by the pilot, experienced a power loss, while in cruise flight, and executed a forced landing on the Bonsilla River approximately 25 miles southwest of Anvik, Alaska. The personal flight, operating under 14 CFR part 91, departed Nulato, Alaska, and the destination was a private airstrip at Kako Mine, Alaska. A visual flight rules flight plan was filed and visual meteorological conditions prevailed. The private certificated pilot and his passenger were not injured and the airplane received substantial damage. According to the pilot, the right tank fuel gauge was indicating full while the left tank fuel gauge was indicating low. The pilot slipped the airplane to see if the gas would move to the left fuel tank and change the gauge indication. He stated the fuel selector was in the both position. Right after the pilot slipped the airplane, the engine stopped producing power. He was unable to restart the engine. The pilot landed on the frozen Bonsilla River and the airplane nosed over during the landing roll. The airplane was equipped with an supplemental type certificate (STC) to allow flight operations with the use of automotive fuel. The pilot stated he fueled from plastic containers just prior to the flight. The pilot did not drain the fuel sumps prior to departure. According to the Pilot's Operating Handbook, in section 4, normal procedures, under preflight inspection, it states for both the right and left wing, "Before first flight of the day and after each refueling, use sampler cup and drain small quantity of fuel from fuel tank sump quick-drain valve to check for water, sediment, and proper fuel grade." Under the "nose" section it states, "Before first flight of the day and after each refueling, pull out strainer drain knob for about four seconds to clear fuel strainer of possible water and sediment. Check strainer closed. If water is observed, the fuel system may contain additional water, and further draining of the system at the strainer, fuel tank sumps, and fuel selector valve drain plug will be necessary." According to the Cessna 172 Pilot's Operating Handbook, under fuel system descriptions, it states the following: "When the fuel selector valve handle is in the BOTH position in cruising flight, unequal fuel flow from each tank may occur if the wings are not maintained exactly level. Resulting wing heaviness can be alleviated gradually by turning the selector handle to the tank in the "heavy" wing." The Handbook further states that with low fuel (1/8th tank or less), a prolonged descent (1500 feet or more) with partial power, full flaps, and 70 KIAS or greater should be avoided due to the possibility of the fuel tank outlets being uncovered, causing temporary fuel starvation.