On May 24, 2014, at 1211 Pacific daylight time, a Cessna 182Q, N97038, experienced a total loss of engine power and force landed in a field one mile south of Arvin, California. During the off airport landing the airplane nosed over, substantially damaging the tail and left lift strut. The airplane was registered to, and operated by, the commercial pilot under the provisions of 14 Code of Federal Regulations, Part 91, as a personal flight. Both the pilot and his single passenger received minor injuries. Visual meteorological conditions prevailed during the flight, and a visual flight plan was not filed. The flight originated at Corona Municipal Airport, Corona, California.The pilot stated that an hour into the flight, while over the Tehachapi Mountains, he noticed that the engine oil pressure had dropped, but the oil temperature and cylinder temperatures were normal. He declared an emergency to Bakersfield Approach and was initially given vectors to Bakersfield Municipal Airport. About 2-3 minutes later he started hearing rattling noises coming from the engine and then the cockpit filled with black smoke. He identified an open field on his left and maneuvered to make that field but didn't realize it had crop furrows. The airplane hit the first berm hard, bounced 3-4 times hitting berms along the way, then the nose wheel hit a berm and flipped the airplane over onto its back. On scene photos showed that the belly of the airplane was coated with engine oil aft of the engine fire wall. An examination of the airplane and engine by the NTSB Investigator-in-Charge (IIC) and a technical representative from Continental Motors Incorporated was performed on September 30, 2014. The engine time indicated on the tachometer was 2,861.6 (hours). Investigators found the air-oil separator return line disconnected from the oil return port located on the rocker cover of the engine's number 1 cylinder. Oil staining was evident on the lower engine cowling below the number 1 cylinder. It was noted that the engine oil filter was located behind the air-oil separator return line. The left engine case half, upper section above the No 4 cylinder, exhibited a 6 x 4 inch hole just aft of the oil filler neck. The cylinders were removed and the case was separated into its halves. The crankshaft main bearings exhibited normal wear with no heat discoloration. The number 3 crankshaft throw bearing was shiny & polished showing very little heat discoloration. The number 4 crankshaft throw was dark black with a few gouges and exhibited extreme heat distress. The number 5 crankshaft throw was black and exhibited extreme heat distress. The number 6 connecting rod attached to the crankshaft throw was discolored dark gray, consistent with heat distress. The internal section of the engine case in line with the number 3 & 4 crankshaft throws exhibited internal repeated impact marks, metal removal, and damage to the oil galleries on both sides of the engine case. Examination of the engine logbook revealed that the most recent annual inspection was performed on April 10, 2013, 2,828.2 hours total time, and 309.5 hours since major overhaul (SMOH). The last entry in the logbook was dated April 18, 2014, where the pilot/owner had performed an oil change, 2,857.3 hours total time