The object of this thesis was to investigate some of the factors that night effect the oil film performance between piston rings and cylinder walls. An apparatus was constructed to measure the instantaneous changes in resistance across the oil film. A piston ring of an air-cooled single cylinder engine was insulated from the rest of the piston using Teflon. A bridge circuit was used to feed the unbalanced signals to an oscilloscope. The traces on the oscilloscope were recorded by means of an Polaroid-Land recording camera. An external motor having a speed control system was used to drive the engine. It was found from this investigation that the lubrication could be improved by increasing the engine speed and oil viscosity. More metallic contact was found when the engine was under its own power. The results also showed that the breakdown of oil film occurred when the oil temperature was increased. The experimental results indicated that the piston ring and the cylinder wall were never separated by lubricating oil at dead centers. The breakdown of oil film occurred at these positions in every case. / Master of Science