On September 8, 1999, at 2140 central daylight time, a Cessna 172, N84385, piloted by a private pilot, received substantial damage during a forced landing after experiencing a loss of engine power. Night visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 personal flight was not operating on a flight plan. The pilot and passenger reported no injuries. The flight departed from Beatrice Municipal Airport, Beatrice, Nebraska, at 2135, on return to Crete Municipal Airport (CEK), Crete, Nebraska. The pilot stated that at 13.6 nmi south-southeast of CEK, at an altitude of 3,500 feet mean sea level, the engine began to run rough and eventually began to windmill. The pilot stated that he checked the magnetos, carburetor heat and mixture. He also stated that the engine was running so rough that it felt as if it had half a propeller and that he could not read the airspeed indicator or altimeter. He circled twice over an unlit gravel road and then touched down twice on the road before impacting a sign. The pilot stated that he made the landing with 15 degrees of flaps and not full flaps since it took two hands to fly the aircraft because of the vibration. Examination of the engine revealed that the engine oil dipstick guide tube was loose which resulted in a loss of engine oil and failure of the #4 connecting rod.