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Lubrication belongs to a system of clean surfaces, correctly fitted parts and appropriate lubricant at specified contacts. Its condition cannot be established just because a watch runs. Lubricants can migrate, change with age or become contaminated; the behaviour depends on their formulation and operating environment. Not every old oil becomes the same abrasive substance, and age alone does not diagnose a particular fault.
Dirt and wear particles at a bearing can contribute to further wear. Insufficient lubricant or unsuitable lubricant can also increase friction or disturb escapement operation. A worn steel pivot and a damaged jewel need individual inspection: it is misleading to describe every fault as an enlarged jewel hole or to assume a photograph reveals the cause. Increased friction may reduce amplitude, but reduced amplitude has several possible causes.
Do not add fresh oil through the back as a general remedy. It does not remove contamination, restore a worn pivot or repair a broken bearing. Excess oil can spread to unintended surfaces, and different movement contacts require different treatment. Household oil, penetrating spray and solvent are not substitutes for a calibre-specific lubrication plan. Avoid touching the hairspring or escapement to test whether something looks dry.
A watchmaker's assessment ordinarily separates cleaning, inspection, necessary repair, assembly and controlled lubrication. The appropriate scope depends on the object and its condition. For a historically significant movement, conservation may favour limited operation or no operation rather than replacing original material purely to make it run. Discuss this aim before work begins and ask for a record of replaced parts and any irreversible treatment.
Unknown service history is a reason for caution, not a licence to invent a service date or interval. Consult the maker's guidance for modern watches and a qualified specialist for historic examples. A fresh invoice should state what was done; a seller's 'serviced' description without detail does not establish a complete overhaul. Do not repeatedly restart a movement that stops, force its winding control or run it solely to demonstrate that it still moves.
A useful collection record identifies the symptoms, operating observations and service evidence separately. State 'runs briefly; lubrication and bearing condition not examined' when that is all that is known. After authorised work, retain the assessment, treatment date and any testing conditions. Preservation of the movement and its evidence is the priority; a short running demonstration is neither a diagnosis nor a guarantee of future accuracy.
What lubrication guides say about ageing oil
The British Horological Institute's guide to lubrication says working surfaces must be thoroughly clean before oiling, to stop the lubricant spreading and deteriorating early. Too much oil overflows and is drawn away from the bearing surface, while oil in the wrong place, such as on wheel teeth, holds dust and speeds up wear. The guide also notes that oils deteriorate under the ultraviolet in daylight, which is why bottles should be kept stoppered, cool but not cold, and in the dark. It contrasts the modern fast-beat watch of 28,800 vibrations an hour, which depends far more on cleanliness and lubrication, with earlier slow-train watches of 18,000 that would keep going, after a fashion, even when completely dry.
The Canadian Conservation Institute describes the sticky dirt on old clock mechanisms as a combination of oil and household dust, which becomes stubborn and hard to shift where too much oil or the wrong lubricant was used. Once dirt and old oil are removed, it adds, the bare metal is very vulnerable to corrosion, so lubrication must follow cleaning as soon as possible and the mechanism should never be run until it is oiled. The Australian Institute for the Conservation of Cultural Material warns that a new lubricant applied without fully removing the old one can react chemically with it and increase degradation, and that many older lubricants, made from sperm whale or porpoise oil, contain acids that accelerate corrosion. It adds that relubricating a worn pivot without polishing or replacing it does not stop the deterioration.
Written from the guidance and records listed under Sources, credited to each publisher and put in our own words; each statement was checked against the cited page.