Originally Posted By: OilUzer
if you plot viscosity vs. temp for example for 5W and 10W, etc. ...
Is the graph linear over the operating temperature?
do companies release these graphs.
Viscosity/temperature is a log/linear relationship. Companies don't generally publish the graphs, but you can plot your own from the viscosities @ 40 and 100°C on log/linear paper. The plot will vary from linear at low temperatures, i.e below about -20°C depending on the chemitry. Better to use an online calculator.