oil pressure drop on 1995 Chevrolet Camaro

oil pressure drops when car is idling after 30 min but small knock in engine

Asked by for the 1995 Chevrolet Camaro
Sounds like either the oil pump is worn and not pumping the correct amount of oil or something is plugging up the oil pick up screen. this is most likely due to sludging in the engine. The oil pan needs to be removed for inspection.