On December 9, 2004, approximately 1512 central standard time, a Mooney M20F single-engine airplane, N3208F, was substantially damaged during a forced landing onto an interstate highway following a reported loss of engine power near Fabens, Texas. The private pilot and his passenger were not injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the personal flight that was operating under the provisions of 14 Code of Federal Regulations Part 91. The cross-country flight originated from the Austin-Bergstrom International Airport (AUS), near Austin, Texas, and made an intermediate stop at the Fort Stockton-Pecos County Airport (FST), near Fort Stockton, Texas. The flight then departed from FST, approximately 1415, with the El Paso International Airport (ELP), near El Paso, Texas, as its intended destination. The 600-hour private pilot reported that when he stopped at FST, he added a quart of oil to the engine for a total of 7 quarts. He then departed, and the flight resumed en route to ELP. The pilot reported that approximately 45 minutes later, he began "having engine difficulties." He said, "the #2 cylinder head temperature gauge was indicating a lower than normal temperature, and shortly thereafter, there was a loss of engine oil pressure." The pilot then determined that there were no available airport landing sites, and few minutes later, the engine stopped. The pilot reported that he prepared to execute an off-airfield emergency landing. He determined that the safest place to land was the westbound lane of Interstate 10, which was directly below him. During the landing flare, the right wing of the airplane collided with the rear of a large semi-tractor truck that was traveling on the highway. The airplane then nosed over and came to rest inverted on the highway. In a telephone interview with an NTSB representative, a witness, who worked at FST, reported that the pilot added oil to the engine prior to his departure from FST. When the airplane took off, the witness observed significant smoke coming from the airplane's exhaust. The witness attempted to contact the pilot three times by radio to tell him what he saw, but was unsuccessful. Additionally, the witness reported that he did not observe any oil on the ground where the airplane had been parked. Examination of the airplane by a Federal Aviation Administration (FAA) inspector ,who responded to the accident site, revealed that there was structural damage to the vertical stabilizer and the right wing of the airplane. The FAA inspector also observed fuel leaking from the fuel tanks. A certificated airframe and powerplant mechanic examined the engine on December 17, 2004, under the supervision of the FAA inspector. The examination revealed that the connecting rod to the # 2 piston was broken. The piston was seized inside of the cylinder and could not be removed. No rod bolts or hardware were found. The fuel injector nozzle for the # 2 cylinder appeared to be partially obstructed. There was damage to the engine case between the #2 and #4 cylinders. The spark plugs were removed and inspected, and no anomalies were found. The oil filter and oil screen were removed, and metal flakes were observed. Oil was not observed on the dipstick or anywhere in the engine, nor did it appear on the exterior surface of the airplane. At 1451, the automated weather observing system at ELP, which was located approximately 22 nautical miles northwest of the accident site, reported wind from 230 degrees at 13 knots, few clouds at 25,000 feet, 10 statute miles visibility, temperature 63 degrees Fahrenheit, dew point 34 degrees Fahrenheit, and an altimeter setting of 30.12 inches of Mercury.