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To reduce the oil consumption in diesel engines, the combination of top ring gap clearance (C1) and second ring gap clearance (C2) (ring gap balance) was applied. The effect of the ring gap balance on piston ring axial motion and second land pressure was observed and factors to control oil consumption were analyzed. The authors obtained a technique to reduce oil consumption by decreasing second land pressure and thus making second ring liable to lift off. Blow up gas was significantly concerned about oil consumption of blow-by gas.

Today preservation of the global environment is an international challenge, and air pollution has attracted more concern than ever. Especially, pollution due to exhaust emission from automobiles is a serious matter, and among others, the improvement of exhaust emission is urgent. For this purpose, regulations have been tightened on exhaust emission such as particulate control and NOx control. Thus, it is essential for oil consumption of diesel engines to reduce oil consumption and employ Exhaust Gas Recirculation (EGR), and piston rings are the important key to solve these problems. This paper clarifies the effect of top rings, among piston rings, on oil consumption through engine tests and theoretical calculation of oil film thickness, and suggests techniques to reduce oil consumption.