Piston oil rings composed of three pieces are commonly referred to as which type?

• A. Segmented
• B. Tapered
• C. Cast
• D. Monolithic

Answer: (A)

Three-piece oil rings are called segmented oil rings. This design uses two thin rails with a spacer between them, forming three pieces that sit in one groove. The segmentation lets the ring assembly flex with piston movement and thermal expansion, maintaining even contact with the cylinder wall and effective oil scraping. The gaps between the segments help regulate the oil film, preventing excess oil from being drawn into the combustion chamber while still providing lubrication where needed. A monolithic oil ring is a single piece and lacks the same flexibility, and the other terms describe different concepts (tapered relates to cross‑section, cast to manufacturing method), not the three-piece arrangement.