EXPLANATION
Rotational viscosity measurements allow the determination of the non-Newtonian, shear thinning property of drain oil. Rotational viscosity values can be compared at a shear rate of 100 s(-1) by this test method. This test method covers the determination of the rotational viscosity and the shear thinning properties of heavy duty diesel engine drain oils at 100° C in the shear range of approximately 0.1 - 10 Pa and the viscosity range of approximately 12 - 35 mPa•s.
TEST SUMMARY
The sample is placed in a controlled stress or controlled shear rate rheometer/viscometer at 100° C. The sample is preheated at 10 s(-1) for 30 s followed by heating at 100° C for 10 min. An increasing shear rate (approximately 10 - 300 s(-1)) or shear stress (0.1 - 10 Pa) sweep is run followed by a decreasing sweep. The rotational viscosity for each step (increasing and decreasing) at 100 s(-1) shear rate is interpolated from the viscosity versus shear rate data table. The rate index, as a measure of shear thinning, is calculated from a plot of In (shear stress) versus In (shear rate).
TEST PRECISION
The precision was found to be dependent on the mean value of the measured property.
Where X is the mean value of rate index, and Y is the mean value of VIS 100 in mPa•s.