Determination of the Cold Flow Behaviour of Multigrade Engine Oils

The relationship between the cold starting and and cold pumpability properties of multigrade engine oils is examined. The reasons why the high shear rate viscosities obtained with the CCS viscometer predicts an oil's startability characteristics but not its pumpability properties are discussed.

The concept of viscosity versus shear rate curves at various temperatures are used to compare engine oils formulated with different VI improvers. Viscosity versus shear rate curves obtained with a pressurized capillary viscometer are compared to those obtained with a rotary viscometer.

Finally, actual oil flow data obtained with a simulated engine gallery was shown to correlate with viscosity data obtained at a selected shear rate.