Piston Ring, Engine

Piston Ring gap
Compression (top) (in gauge) 0.25-0.50 mm (0.01-0.02 in)
Compression (bottom) (in Gauge) 0.25-0.50 mm (0.01-0.02 in)
Oil ring (steel rail) (in Gauge) 0.25-1.25 mm (0.010-0.049 in)

Side clearance
1st ring 0.040-0.095 mm (0.0016-0.0037 in)
2nd ring 0.040-0.095 mm (0.0016-0.0037 in)