A three-piece oil ring in which sealing performance is enhanced and lubricant consumption is reduced even with low tension and thin width, and occurrence of sticking is eliminated. A combination of three- piece oil ring and a piston is also provided. The three-piece oil ring has a spacer expander (10) and two side rails. The spacer expander (10) has lug portions (13) respectively projecting in the axial direction in order to press the respective inner circumferences of first and second side rails on the radial inner side and each having a bevel on the radial outside, and side rail supporting portions (14) respectively projecting in the axial direction in order to support the axial end faces of the first and second side rails at the radial outer position. Lug angle between the bevel (13a) on the radial outer side of the lug portion and the axis is 10°-20°, and the ratio 2X/Y between the total distance 2X of respective axially projecting distances X of the side rail supporting portions and the distance Y between the axial end faces of both lug portions is in the range of 0.04-0.15.
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