Why Get an Old Watch Serviced When It Runs Fine?

This is a nice example of why watches need service and cleaning, especially old watches that are said to "run fine", but have not been serviced in decades. Dirt sticks in old oil and turns gritty, and in a watch, which has parts that turn, a lot, this grit wears. A watch that runs fine, may in fact have not problems, at the moment, but running a watch without getting it serviced is just like running a car without changing the oil.

Here the upper pivot of a center wheel has a grove cut so deeply into the side that the wheel no long fully engages with its partners in the train. It has to be replaced.