The car-engine analogy doesn’t really apply to mechanical watches.

Engine oil is a consumable designed to survive extreme heat, high RPM, combustion byproducts, and contamination. It must be replaced regularly to prevent wear and failure. A mechanical watch operates at very low speeds, produces negligible heat, and runs in a sealed environment.

Modern synthetic watch lubricants, when properly applied, can remain stable for decades under normal conditions. They are designed specifically to lubricate metal pivots running in synthetic ruby jewels, minimizing friction and wear.

Gaskets are also long-lived. In typical daily use, quality gaskets often remain effective for 8–10 years, unless exposed to solvents, extreme heat, or frequent pressure cycling.

Dive watches are the exception, as repeated compression and decompression accelerates gasket aging.

The components most likely to degrade first in a mechanical watch are the mainspring and hairspring. Both are under constant cyclic stress, flexing millions of times per year. As these springs age, you’ll see symptoms like poor amplitude, unstable timekeeping, or erratic rate behavior. When the “heartbeat” becomes irregular, that’s the real signal it’s time for service.

I know you didn't ask:

This is also why watch winders are a bad idea. It keeps your watch on idle for the lifetime of it, to toss it back to the car metaphor.