Piston Ring, Engine

Piston ring end gap
Compression (top, gauge diameter) b 0.100 - 0.250 mm (0.0039 - 0.0098 in.)
Compression (bottom, gauge diameter) 0.27 - 0.42 mm (0.0106 - 0.0165 in.)
Oil ring (steel rail, gauge diameter) 0.15 - 0.65 mm (0.0059 - 0.0255 in.)
Compression (top, service limit) 0.50 mm max (0.0196 in.)
Compression (bottom service limit) 0.65 mm max (0.0255 in.)
Oil ring (steel rail, service limit) 0.90 mm max (0.0354 in.)
Piston ring groove width
Compression (top) 1.230 - 1.245 mm (0.0484 - 0.0490 in.)
Compression (bottom) 1.530 - 1.545 mm (0.0602 - 0.0608 in.)
Oil ring 3.030 - 3.055 mm (0.1192 - 0.0120 in.)

b Specification 82.4 mm (3.2441 in.) diameter gauge