Oil Selection by Point

Lubrication in a watch movement is not a single undifferentiated task but a set of distinct decisions, because the points being lubricated differ enormously in load, speed, temperature exposure and the metals in contact. A fast-turning, lightly loaded balance-staff pivot needs a lubricant that stays put on a very small jewel surface without spreading and that resists breaking down under the very high number of oscillations it will experience; a slow-turning, heavily loaded barrel arbor or mainspring coil needs a heavier, higher-viscosity lubricant, or in the case of the mainspring itself, a specific spring lubricant or braking grease formulated to reduce friction between the coils as the spring breathes.

Manufacturers and lubricant suppliers publish viscosity grades and specific product lines aimed at particular point categories: light oils for balance and pallet-jewel pivots, medium oils for train-wheel pivots, heavier oils or greases for the barrel arbor and mainspring, and specialised greases (often molybdenum-disulphide-based) for the keyless and motion work, where sliding friction between gear teeth and levers, rather than pure rotational bearing friction, predominates. Using a heavy oil where a light one belongs can noticeably slow a delicate pivot and reduce amplitude; using a light oil where a heavy one belongs can allow it to migrate away from a heavily loaded surface too quickly, leaving the point running dry well before the next service.

Quantity matters as much as type: watch oils are applied in exact, tiny, calibrated amounts using a fine oiler dipped to a specific depth, guided by the jewel's oil sink (a shallow, saucer-like recess machined around many jewel holes specifically to hold a controlled amount of oil in place by surface tension). Too little oil starves the bearing and accelerates wear; too much oil can migrate along a pivot or wheel by capillary action, spreading onto the hairspring or escapement and causing exactly the kind of gumming and rate disturbance that a service is meant to prevent.

Oils also age differently depending on their formulation and where they sit: light pivot oils have historically been prone to gradual thickening, oxidation and evaporation of their more volatile fractions over years, which is the underlying physical reason routine servicing intervals exist at all, while modern synthetic watch oils are formulated for improved stability but are not considered permanent or maintenance-free. Understanding lubrication as a set of point-specific engineering decisions, rather than one generic 'oiling' step, is central to understanding why a proper service is a substantially more considered process than simply squirting oil into an open movement.

This lesson deliberately stays at the level of reasoning and vocabulary a well-informed owner needs, rather than a product-by-product application guide, because correct oil selection and quantity for a specific calibre is technical, manufacturer- and supplier-specific knowledge that a trained watchmaker applies using current lubrication charts, and is not something to improvise from general description alone.