Walther Viscosity–Temperature Equation

Predict viscosity at any temperature given two reference viscosities using the ASTM D341 (Walther) relation.

FuelViscosity

Viscosity at T₁cStT₁°CViscosity at T₂cStT₂°CTarget temperature T°C

Viscosity at target T: 67.9cSt

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Formula, assumptions, and limits

\log_{10}[\log_{10}(\nu + 0.7)] = A - B \cdot \log_{10}(T)

Symbol	Meaning	Unit
$ν$	Viscosity	cSt
$T$	Temperature	K
$A, B$	Fuel-specific constants

Source: ASTM D341

In short

Predict viscosity at any temperature given two reference viscosities using the ASTM D341 (Walther) relation.

Learn the theory Bunker Quality and ISO 8217 Marine Fuel Standards