| abstract |
A multi-piece oil ring is provided in which, even after long-term operation of an engine, adhesion and deposition of oil sludge are prevented, sticking of components does not occur, and a high oil control function can be maintained. The multi-piece oil ring includes a spacer expander and a pair of upper and lower side rails supported by the spacer expander. To achieve the above features, at least side faces of the side rails that face the spacer expander are coated with a fluorine-containing coating, and the spacer expander is coated with a metal coating. The angle of contact (θ 1 ) of a paraffin-based lubricating oil with the portions of the side rails at 150°C that are coated with the fluorine-containing coating is 50° or larger, and the angle of contact (θ 2 ) of the paraffin-based lubricating oil with the portion of the spacer expander at 150°C that is coated with the metal coating is 10 to 50°. The difference between θ 1 and θ 2 (θ 1 -θ 2 ) is 30° or larger. |