EXPLANATION
This test method evaluates the percent viscosity loss of fluids resulting from physical degradation in the high shear nozzle device. Thermal or oxidative effects are minimized. This test method may be used by manufacturers of polymeric lubricant additives and their customers. This test method is not intended to predict viscosity loss in field service in different field equipment under widely varying operating conditions, which may cause lubricant viscosity to change due to thermal and oxidative changes, as well as by the mechanical shearing of polymer. However, when the field service condition, primarily or exclusively, result in the degradation of polymer by mechanical shearing, there may be a correlation between the results from this test method and field results.
This test method measures the viscosity loss, in mm2/s and percent, at 100° C of polymer-containing fluids when evaluated by a diesel injector apparatus procedure that uses European diesel injector test equipment. The viscosity loss reflects polymer degradation due to shear at the nozzle. Viscosity loss is evaluated after both 30 and 90 cycles of shearing. In general, there is no correlation between results after these two cycles of shearing. Test Method ASTM D6278 uses essentially the same procedure with 30 cycles instead of both 30 and 90 cycles. The correlation between results from this test method at 30 cycles and results from Test Method ASTM D6278 has not been established. Test Method ASTM D2603 has been used for similar evaluation of shear stability. No detailed attempt has been made to correlate the results of this test method with those of the sonic shear method. This test method uses test apparatus as defined in CEC L-14-A-93; however, they differ in the period of time required for calibration. Test Method ASTM D5275 also shears oils in a diesel injector apparatus, but may give different results. This test method has different calibration and operational requirements than Test Method ASTM D3945.
TEST SUMMARY
A polymer containing fluid is passed through a diesel injector nozzle at a shear rate that may reduce its kinematic viscosity. The percent viscosity loss is a measure of the mechanical shear stability of the fluid. This test method may also be used for oils not containing polymer. It might not be known whether an oil submitted for test contains a polymer.
TEST PRECISION
Based on limited interlaboratory test results following preliminary precision was found. Further more extensive study is underway.
All test results are relative to those of the calibration fluid. Therefore no estimate of bias can be justified.