Abstract: An oil ring for a piston of an internal combustion engine is provided. The oil ring is disposed in a ring groove of the piston and includes a counterbore along an inner diameter surface. A land in the piston which is located above the ring groove containing the oil ring includes a plurality of holes extending radially inwardly to the ring groove behind the counterbore of the oil ring. During operation, the oil ring will be energized during the power stroke by channeling combustion pressure from the piston land above the oil ring through the holes and to the area in the ring groove behind the oil ring. The oil ring is not energized during the remaining strokes, which results in a reduction of oil ring friction while still maintaining oil film control.

Abstract: A piston ring assembly for sealing a cylinder wall to a piston body is provided. The piston ring assembly includes a plurality of rings stacked in an axial direction one in abutment with another. Each ring has an inner face and an outer face. The piston ring assembly also includes a spring which substantially circumferentially surrounds the stacked rings and abuts the outer faces of the rings. The spring biases the stacked rings in a radially inward direction for sealing the inner faces of the rings against the piston body. The spring may be of a strip of material bent into a serpentine pattern when in an at rest condition to apply the biasing force against the piston body.