Viscosity at temperature T from VI — ISO 2909/ASTM D2270 + ASTM D341 (reference case)
Kinematic viscosity at an arbitrary temperature T, derived from the Viscosity Index (ISO 2909/ASTM D2270) and interpolated per ASTM D341, for one worked reference oil (40°C/68 cSt, VI=97, evaluated at T=100°C). The original page never ships the combined formula client-side — only this login-gated worked example.
docs/calculator-classification.csv lists iso_3348 as locked=false, but the source (ISO_3348.js) contains the identical "Please login to get full access!" demo gate found in the other five locked lubricant calculators. Treated here as locked, consistent with the actual source rather than the classification label. No formula in this source to generalize.
Method & references
- ISO 2909 / ASTM D2270 Viscosity Index combined with ASTM D341 (Ubbelohde-Walther) interpolation to get viscosity at an arbitrary temperature.
- The legacy client-side source contains no such combined formula: n3 is a literal constant (8.6) assigned unconditionally, only ever gated 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-at-temperature calculator.
The computation is a literal port of the original client-side JavaScript from /calculators/iso_3348.htm. Results are verified equal to the original by an automated golden-master test. No formula has been re-derived or “improved”.