The effect of the cylinder bore deformation and piston ring tension on oil consumption was investigated under engine operating condition. At the cylinder upper area, the second order deformation caused by thermal expansion and the fourth order deformation due to head bolts showed good agreement with oil consumption using low-tension-ring. In the case of high-tension-ring, however, the correlation-coefficient between the cylinder deformation and oil consumption was lower than that of low-tension-ring. It was also found that the fourth order deformation at the lower area of cylinder showed good correlation with oil consumption.