The private pilot was returning to his departure airport after a local area flight when the engine failed as he was preparing to enter the traffic pattern. The pilot stated in an interview that he noticed the engine revolutions per minute at the red line and that it could not be controlled by the propeller lever. The pilot declared an emergency and within approximately 30 seconds the engine failed and the propeller stopped. During the forced landing, while the pilot attempted to align the aircraft with the runway, the left wing contacted the ground and the aircraft slid to a stop near the end of the runway. The pilot was not injured and the airplane sustained substantial damage to the left wing. An on-scene investigation conducted by a Federal Aviation Administration inspector revealed that the engine sump did not contain oil. It was determined that the oil cooler interconnect line on the left oil cooler was only finger tight, which resulted in an oil leak and subsequent loss of all engine oil. No other leaks were found and no other engine anomalies were noted.