SwRI: Foaming evaluation procedure is an API CJ-4-approved test used to evaluate foaming-related problems in lubricant oils that can lead to mechanical failure such as inadequate lubrication, cavitation, and overflow loss of lubricant.

	High-shear viscosity evaluation equipment
	Two oils, calibration oil and non-Newtonian reference oil, are used to determine the gap distance between the rotor and stator so that a shear rate of a 1 ?106 s-1is maintained.

The high-temperature, high-shear viscosity evaluation procedure conducted at Southwest Research Institute is an API CJ-4-approved test. This evaluation method tests oil viscosity at the shear rate and temperature thought to be representative of the condition encountered in the bearings of automotive engines in severe service.

High-Temperature, High-Shear Viscosity Evaluation Equipment and Procedure

This test method covers the laboratory determination of the viscosity of engine oils at 150°C and 1 × 10⁶ s^-1 shear rate using a tapered bearing simulator-viscometer (TBS Viscometer) equipped with a refined thermoregulator system.

A motor drives a tapered rotor that is closely fitted inside a matched stator. The rotor exhibits a reactive torque response when it encounters a viscous resistance from an oil that fills the gap between the rotor and stator. Two oils, calibration oil and non-Newtonian reference oil, are used to determine the gap distance between the rotor and stator so that a shear rate of a 1 × 10⁶ s^-1is maintained. Additional calibration oils are used to establish the viscosity / torque relationship which is required for the determination of the apparent viscosity of test oils at 150°C.

High-Temperature, High-shear Viscosity Evaluation Test Method

A viscometer consisting of a synchronous two-speed motor that drives a slightly tapered bearing in a matched stator is used. A console contains the power source for the:

• Load cell

• Thermoregulator circuit

• Heating coil

• Motor

The console also contains:

• Circuitry for regulating and monitoring the temperature of the oil in the test cell

• Amplifier

• Digital readout of the load cell response

A flow of dry compressed air is passed around the stator to provide supplementary cooling when testing fluids of higher viscosity. Ports are provided in the stator housing for the circulation of compressed air. A 50-mL glass syringes, with a filter, equipped with Leur needle lock, fits the top of the filling tube for injection of test oil into the test cell.

Pass/Fail Criteria

The pass/fail criteria for the high-temperature, high-shear viscosity evaluation procedure has been established as Viscosity @ 150C, min and 3.5 cP.

For more information about the high-temperature, high-shear viscosity evaluation capabilities at Southwest Research Institute (SwRI) or how you can contract with SwRI, please contact Becky Grinfield at bgrinfield@swri.org or (210) 522-3652.