Lubrication is the critical point of every overhaul: wrong oil, wrong location, or wrong quantity compromises precision more than any mechanical wear. I learned this at Piaget in 1974, on ultra-thin calibres where there was zero room for error.
Natural oils — neatsfoot, whale spermaceti — dominated until the Fifties, when Moebius introduced synthetics like Synt-a-Lube 9010. The shift was radical: natural oils thickened within months, synthetics last years. This single fact changed overhaul frequency. But durability isn't infinite: each calibre has its own lubrication chart, a schema signed by the maker that specifies which oil, at which point, in which quantity. It's not a detail: it's the reference document I still open at the bench today, after fifty years.
Escapement friction is the costliest problem in energy terms. The traditional Swiss lever — born from Mudge in 1755 — transmits less than 33% of the barrel's energy, precisely because of friction between the pallets and the escape wheel teeth. It requires constant lubrication, and when the oil degrades, stability collapses. Breguet already intuited the opposite direction in 1789 with the natural escapement, theoretically exempt from lubrication. George Daniels reread that intuition in the Co-Axial he patented and then sold to Omega in 1999: tangential impulse instead of radial, reduced friction, extended maintenance intervals.
The next step was eliminating oil entirely. Silicon is self-lubricating by nature: its surface reduces friction without chemical additives, doesn't corrode, is lightweight and non-magnetic. When Ulysse Nardin mounted the first silicon parts in the Freak at the turn of the 2000s, the point wasn't aesthetics: it was removing oil from the equation. Patek Philippe with Silinvar, IWC with Diamond Shell on the Portugieser tourbillon — diamond coating on silicon components — and Sinn with DIAPAL technology in 2001 follow the same logic: no oil to change, no programmed degradation.
Then there's a use of lubrication that doesn't concern the movement: Ressence fills the upper chamber of the Type 3 with 35.7 ml of oil not to lubricate in the strict sense, but to eliminate optical refraction between disc and sapphire crystal. The oil also lubricates the ROCS system, but the primary reason is optical. It's a case where the fluid changes function without changing nature.
The mi-glace finish on rubies — rounded surface rather than flat, among the Geneva Seal criteria — also improves oil retention at the contact point. A finishing detail with direct functional consequences.