What happened
During flight, the pilot notified Air Traffic Control (ATC) that the engine oil pressure was dropping and subsequently reported that the engine was overheating. The pilot requested vectors to the nearest airport; however, radio and radar contact were lost while the aircraft was descending, approximately 10 miles east of the airport.
The aircraft eventually touched down on a westerly heading in a field located about 5 miles east of the airport. The pilot reported that maintenance personnel had changed the engine oil at his hangar the previous day, making this the first flight following the maintenance work. An engine run-up had not been performed after the oil change due to inclement weather.
The investigation
An examination of the engine identified that an 'O' ring seal (P/N CI48100-8) installed on the cap of the oil filter had been pinched during installation. This defect allowed engine oil to leak during operation.
Engine records indicated that the engine had been modified on December 5, 1995, with the installation of an 'Ultimate Engine Oil Filter' (Part number SA8922SW21) manufactured by Capehart Industries Inc. of Mena, Arkansas, under an FAA Supplemental Type Certificate dated July 21, 1994.