Which type of piston oil ring is made of three pieces?

• A. Wedge
• B. Segmented
• C. Spiral
• D. Solid

Answer: (B)

Piston oil rings are designed to control the amount of oil that coats the cylinder wall and to return excess oil to the sump. The type made of three pieces is the segmented oil ring. It consists of two thin rails that ride against the cylinder wall and a spacer (sometimes called an expander) between them. This spacer keeps the rails separated and provides the correct spring tension, so the ring can conform to the bore and maintain effective oil scraping and return across temperature and wear.

This three-piece design lets the ring flex and follow the piston as it moves, helping to seal without binding and to regulate oil film more precisely. Other designs mentioned—wedge, spiral, and solid—are typically single-piece configurations with different cross-sectional shapes or wound patterns, not assembled from two rails plus a spacer.