A watch service — also called an overhaul — is the periodic maintenance procedure that a mechanical watch requires to continue functioning correctly over time. Unlike a quartz watch, which needs only a battery change and occasional regulation, a mechanical movement has dozens of moving parts that require lubrication to reduce friction and wear. That lubrication degrades with time and use, thickening, drying, or migrating away from where it is needed. A movement running on degraded lubricants will lose amplitude, keep poor time, and eventually stop or sustain wear damage.

A full service involves complete disassembly of the movement: every wheel, jewel, spring, lever, and plate is removed, cleaned ultrasonically, inspected for wear, and dried. Worn parts are replaced. The movement is then reassembled with fresh lubricant applied to each friction point in precise, measured quantities — too little oil and friction returns; too much and it migrates where it should not. Once reassembled, the movement is regulated on a timing machine, checked in multiple positions, and ideally worn or run for several weeks before final regulation confirmation.

How often a watch needs servicing depends on the movement, the conditions of use, and the owner's performance expectations. Most manufacturers recommend between three and five years for sport and complicated watches, and five to eight years for simpler movements worn occasionally. In practice, many well-made movements will run for a decade between services without catastrophic failure, but at the cost of some accuracy degradation and increased internal wear. Keeping to a reasonable service schedule is the single most important thing an owner can do for the long-term health of a mechanical watch.