Temperature Dependence of Viscosity

[DavidMBrown]

I am in need of equations describing the temperature dependence of viscosity of various motor oils, hydraulic oils, gear oils, and ATFs. Typically, product data sheets only give the viscosity at 40 C. There are graphs available that show an approximately log-linear dependence of viscosity with temperature, but the log scale of viscosity on these graphs is not uniform, ie, the distance between decades varies.

Does anyone have the mathematical basis for these graphs, ie, an equation for viscosity versus temperature given one viscosity, temperature data point for a particular product?

Thank you,
David Brown
The Fourth River Company
Pittsburgh, PA