Viscosity Index — ISO 2909 / ASTM D2270 (reference case)
Viscosity Index (VI) and its two inverse forms (kinematic viscosity at 100°C, or at 40°C) for one worked reference oil (40°C/68 cSt, 100°C/8.6 cSt, VI=97). The original page never ships the VI formula client-side — only this login-gated worked example, in three directions.
All three VI-related solves are unconditional-constant outputs, like astm_d341.js and unlike vogel-cameron.js/oil_mixture.js/barus_roelands.js (which blank on mismatch). No formula in this source to generalize — reimplementing the real ISO 2909/ASTM D2270 Viscosity-Index equation from an external reference was explicitly avoided per the migration correctness rules.
Methode & referenties
- ISO 2909 / ASTM D2270 — Viscosity Index of petroleum products, and its two inverse forms.
- The legacy client-side source contains no VI formula: each output is a literal constant, gated only by a login-upsell alert that resets the visible inputs, not the result. This port is faithful to that: it is not a general Viscosity Index calculator.
- The file also embeds a fourth function, a byte-for-byte duplicate of astm_d341.js's ASTM D341 interpolation (same inputs, defaults and hardcoded 28.5 result) — intentionally not re-ported here; see astm-d341-viscosity-temperature.ts.
De berekening is een letterlijke overzetting van de originele client-side JavaScript van /calculators/astm_d2270-226.htm. Resultaten zijn geverifieerd gelijk aan het origineel via een geautomatiseerde golden-master-test. Geen enkele formule is opnieuw afgeleid of “verbeterd”.