On January 5, 2013, about 1300 Pacific standard time, an experimental Jeremiah Jackson Vans RV-10, N262NJ, made an off-field forced landing near Julian, California. The pilot/owner was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The private pilot sustained minor injuries; the airplane sustained substantial damage from impact forces. The local personal flight departed Ramona, California, about 1045. Visual meteorological conditions (VMC) prevailed, and no flight plan had been filed.The pilot reported that the airplane was in phase one flight testing. The airplane and engine had a total time of 6 hours, and this was the fourth test flight. He was about 2 hours into his flight, and heading toward his home airport with the airplane level at 8,500 feet mean sea level. He observed the oil pressure go down rapidly to about 5 pounds per square inch (psi), but did not notice any other problems with the airplane or engine. He declared an emergency, and requested a direct approach to Ramona airport, runway 27. Within 5 minutes, the engine lost all oil pressure, and the engine seized. He was unable to make any available airstrips, and observed a steep gorge ahead of him. He turned, and elected to land on a winding dirt road on top of a ridge. He avoided trees and cars parked at a trailhead, but the airplane hit a steep embankment. The airplane sustained substantial damage to the fuselage and wings. A Federal Aviation Administration inspector examined the wreckage. He observed that an oil line just to the right of the oil filter was disconnected. Oil sprayed into the cowling, and exited out the lower nose at approximately the 5:30-6 o'clock position. The pilot stated that there were no indications of oil leakage during the preflight inspection.