fluid duty
also called what job it does in the machine
What job the substance does inside the machine — lubricating an engine, lubricating a gearbox, working an automatic transmission, carrying hydraulic power, working the brakes, cooling an engine, lubricating a bearing, lubricating a chassis joint. It is the fact that makes a service fluid the thing it is, and it is deliberately CARDINALITY MANY, because real products carry several duties at once: TotalEnergies publishes Rubia SX 40 as a 'Monograde mineral lubricant, suitable for hydraulic circuits, engines and gearboxes', and one Dar es Salaam duka's own note for a 4 L pack reads 'Hydraulic oil (Gearbox Oil)'. That many-ness is the whole reason engine oil, gearbox oil, hydraulic oil, transmission fluid and brake fluid are VALUES here and not classes: a class would force one product into one box that its own maker refuses. Distinct from b153's `filtration_duty`, which names the substance a FILTER cleans (and includes petrol, diesel, intake air and cabin air, none of which is a service any fluid performs); this names the service a SUBSTANCE performs, and no value of one belongs in the other. It is intrinsic and NOT a fitment (REFINE-LOG 2026-08-25): no vehicle is named and nothing about the oil changes when a model is discontinued. Concern identity, so NOT axis-eligible: an engine oil and a brake fluid are two listings, never two cells of one buy box.
Fluid duty is answered with one word chosen from the fluid duties list — the same word shared across every product that uses it.
It belongs to identity — who and what it is.
asked by the kinds that answer it
3 kinds answer it, each for one or more values. The same question can be reused by unrelated kinds — one meaning, many homes.
asked by kinds that answer it
The same question can be reused by unrelated kinds — one meaning, many homes.
| kind | how many |
|---|---|
| service fluid | required · many |