Low Shear Viscometry and Cold Flow Mechanism - Engine Oils

The viscosity-shear dependence of multiviscosity oils measured in a rotary viscometer at low shear rates fits the Power Law model, relating viscosity to shear rate. A simulated oil pan rig permitted calculation of critical shear conditions and viscosities for engine pumpability. Critical conditions of apparent viscosity and shear stress were computed to be 400 poise at 5000 dynes/cm² from data on a series of ASTM reference pumpability oils.