viscosity grade
also called grade · thickness grade
The place a service fluid occupies on its trade's own published thickness scale — an SAE J300 grade for an engine oil (20W-50, 5W-30, SAE 40), an NLGI consistency grade for a grease (NLGI 2), an ISO VG number for an industrial hydraulic oil (ISO VG 46). One property and not three, because it is one question — 'how thick is it, on the scale this trade grades by' — wearing three surface names, and the answer is always a place on a CLOSED published scale. Which scale is the `grading_scale` qualifier, and it must be stated, because NLGI 2 and ISO VG 2 are both spelled '2' and mean opposite things. Deliberately OPTIONAL, and that is evidence-led: an automatic-transmission fluid has NO viscosity grade at all — Toyota Type WS, Type T-IV, DEXRON III and Nissan CVT NS-3 publish kinematic viscosity, a viscosity index and a named fluid specification, and no grade of any kind. Its measured counterpart is `kinematic_viscosity`; a grade is the merchandising axis, the mm2/s figure is the measurement. Concern measurement, so axis-eligible: 5W-30 and 20W-50 of the same product line are genuinely versions of one listing, the way 24 oz and 32 oz are for a bottle.
Viscosity grade is answered with one word chosen from the viscosity grades list — the same word shared across every product that uses it.
It belongs to measurement — its measurable, physical facts.
the bundle what travels with each viscosity grade
A viscosity grade is not a lone value — each statement is a self-correlating bundle, carrying its own:
asked by the kinds that answer it
3 kinds answer it, each for a single value. 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 | one |