An engine in which an oil consumption and a leakage of blow-by gas can be stably reduced for a long period of time. The engine includes a first land (3), a first ring groove (4), a second land (5), a second ring groove (6), a third land (7), a third ring groove (8), and a piston skirt (9) formed on a piston peripheral wall (1) in the above-recited order from a side of a piston head (2). A first pressure ring (10) is fitted in the first ring groove (4). A second pressure ring (11) is fitted in the second ring groove (6), an oil ring (12) fitted in the third ring groove (8), and an indentation (13) is formed at the second land (5).