On October 28, 2020, about 1140 eastern daylight time, a Cessna 182T airplane, N3537C, was substantially damaged when it was involved in an accident near Lebanon, Ohio. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that he and the passenger were on a cross-country flight from Clermont County Airport (I69), Ohio, to Warren County Airport (I68), Ohio, after maintenance was performed to install new avionics the day before. While level at 3,000 ft mean sea level (MSL), in instrument meteorological conditions, the oil pressure dropped to zero. The engine initially ran smooth after the drop in oil pressure, but then it began to knock and vibrate. The pilot declared an emergency with air traffic control, proceeded direct to I68, but was unable to maintain altitude. The airplane descended below the clouds about 600 ft above the ground and the engine lost all power. Unable to make the runway, the pilot landed in a harvested corn field. The pilot could not stop the airplane before it hit trees at the end of the field; the airplane’s wings and fuselage sustained substantial damage. The engine was examined, and a brightly colored plastic cap was found installed on the crankcase breather port, which completely blocked the port. The engine crankcase seal on the front of the engine was found dislodged and oil was found on the underside of engine compartment and cowling. The purpose of the crankcase breather port is to vent engine pressure. The crankcase seal provides the next location for pressure to vent if the breather port becomes blocked. The Federal Aviation Administration visited the repair station that installed the avionics on the airplane. They determined that the mechanic also performed maintenance on the engine which was outside of the repair station’s operations specifications. The mechanic did not have the technical data for the work performed. Further, the mechanic did not document the maintenance that he performed in the engine maintenance logbook. Maintenance records documented the installation of a Garmin avionics suite at the repair station. The last entry in the engine maintenance logbook was an oil change dated September 23, 2020.