The reduction of engine oil consumption rate is one of the important concerns for automotive engineers. However, it has been difficult to solve this subject, since the oil consumption mechanism has not yet been elucidated.In this study, to clarify the oil loss mechanism via the piston rings, a transparent glass cylinder engine was used to observe oil behavior between cylinder wall and piston surface. For photographic observation, a high speed camera, a still camera. and a TV camera were used. Since the new photographic system by using TV camera with a synchro - flash and a synchro-memory was applied, it was also possible to observe the oil behavior in detail.Moreover, a new visual method by which colored oil was injected from the various points on the piston surface and traced was developed for easy analysis of oil movement around the piston ring.Results obtained for this visualization indicated that oil was mainly drawn into the combustion chamber through the gap areas in compression ring joints at high vacuum generated under engine braking conditions and the oil passing over the peripheral surface of the oil control ring was more apparent when the piston rotational movements were greater.