THE EFFECT OF ENGINE OPERATION ON THE VLSCOMETRIC PROPERTIES OF MULTIGRADED ENGINE OILS 650445
It has long been known from various sonic and mechanical shear tests that most commercial multigraded oils suffer from a serious loss in viscosity during relatively short periods of use. These tests, except in special cases, were generally regarded as inadequate. In order to conduct a meaningful study of the effect of shear degradation on polymer-containing oils, the authors set up an engine test.
The test, over a period of several months using three engines almost daily, proved reliable beyond all expectations. Tests of 15 different multigrade oils showed that seven did not qualify as SAE 30 oils after a running period equivalent to about 385 miles. All the remaining oils showed significant losses in viscosity in the same period.
The effect of shear degradation on the 0°F measured viscosity was varied. Most of the oils showed a proportionately lower viscosity loss measured at 0°F than at 210°F. Complicating factors indicate that the area merits further investigation.