Viscosity-temperature relation — ASTM D341 (reference case)

ASTM D341 (Ubbelohde-Walther) kinematic viscosity-temperature interpolation for one worked reference oil (40°C/68 cSt, 100°C/8.6 cSt, interpolated to 60°C). The original page never ships the interpolation formula client-side — only this login-gated worked example.

✓ validated against legacyoriginal: /calculators/astm_d341.htm

Viscosity-temperature relation — ASTM D341 (reference case) — original diagram from /calculators/astm_d341.htm

Reference temperature, T₁°CViscosity at T₁, ν₁cStReference temperature, T₂°CViscosity at T₂, ν₂cStTarget temperature, T₃°C

Interpolated viscosity at T₃, ν₃28.5 cSt

The demo lock in this file differs from vogel-cameron.js: on mismatch it resets the input fields but still unconditionally sets the output to 28.5 (it does not blank it). There is no formula in this source to generalize — reimplementing the real ASTM D341 equation from an external reference was explicitly avoided per the migration correctness rules.

Method & references

ASTM D341 — Ubbelohde-Walther viscosity-temperature interpolation for petroleum products.
The legacy client-side source contains no interpolation formula: n3 is a literal constant (28.5) 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 interpolation calculator.

The computation is a literal port of the original client-side JavaScript from /calculators/astm_d341.htm. Results are verified equal to the original by an automated golden-master test. No formula has been re-derived or “improved”.

Viscosity-temperature relation — ASTM D341 (reference case) — Engineering ABC