At approximately 1512 Central time, the airplane was substantially damaged during a forced landing on an Interstate highway following loss of engine power. The Private pilot and his passenger were not injured. Visual conditions prevailed; the flight originated at Austin, Texas, and made an intermediate stop near Fort Stockton, Texas. The flight then departed at approximately 1415, with the El Paso (Texas) International Airport as its final destination. While on the ground at Fort Stockton, the pilot added a quart of oil to the engine, for a total of seven quarts. Approximately 45 minutes later, the pilot noticed 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 determined that there were no available nearby airports and, a few minutes later, the engine stopped. The pilot determined that the safest place to land was the westbound lane of Interstate 10 below him. During the landing, the right wing collided with the rear of a large truck. The airplane then flipped over and came to rest inverted.