On December 30, 2002, at 1148 Pacific standard time, an experimental Nicholson Lancair 320, N364M, experienced a loss of oil pressure during climb, and made a forced landing on Interstate 15, south of the 91 freeway and Interstate 15 interchange, near Corona, California. The airplane sustained substantial damage when it collided with a motor home during the final approach. The pilot/builder/owner operated the airplane under the provisions of 14 CFR Part 91. The pilot, the sole occupant, was not injured, and there were no ground injuries. Visual meteorological conditions prevailed for the local cross-country flight that departed the Chino Municipal Airport (CNO) at 1130. The flight was scheduled to terminate at the French Valley Airport (F70), Murrieta/Temecula, California, and no flight plan had been filed. The pilot reported that he had installed an air/oil separator the day before the accident. To install the air/oil separator he removed one end of the high-pressure oil line to the oil cooler. After the unit was installed, he reattached and "firmly tightened" the screw clamp as "best he could." He then taxied the airplane with the engine cowling off for a 1/2 hour to check for oil leaks. The pilot stated that on the day of the accident, there was "the usual taxi and warm-up" prior to takeoff. No discrepancies were noted with the oil pressure gage during this time. The pilot departed CNO, and was at 6,500 feet en route to F70 when he started to smell oil in the cockpit. The pilot looked at his gages and noted that he was losing oil pressure. He decided to make an emergency landing on the Interstate. On final approach, the engine seized, and the airplane struck the roof of a motor home and came to rest on its belly. According to the pilot, the engine seized after the "hi presssure oil line to oil cooler was pushed or pulled off, draining all oil" from the engine.