ASTM International

SHEAR STABILITY OF MULTIGRADE CRANKCASE OIL Establishment of Field Data and Correlation with Laboratory Engine and Bench Test Results
 N DS49

Annotation

SUMMARY

Extensive field test data have been obtained which can serve as a basis for evaluating the ability of various laboratory methods to predict the shear stability of multigrade crankcase oils. This basis was developed by determining the average viscosity changes of one single grade and twelve multigrade reference oils in six separate car fleets. The twelve multigrade oils were formulated with all of the chemical types of VI improvers currently in use, or likely to be used, in the near future.

As a second part of the program, four types of bench tests and three different laboratory engine tests were evaluated for their ability to predict the average viscosity changes of the thirteen reference oils observed in the fleet tests. Correlation of the laboratory methods results with the field data was marred by the non-conformance of two multigrade oils. This non-conformance was more noticeable in the bench test results than in the laboratory engine test data.

The control oil (ARO-113) which did not contain a VJ. improver, showed a measurable viscosity increase in the 1500 mile field tests. This indicated that factors other than mechanical shear may have influenced the viscosity changes of the multigrade oils in the field tests. Consequently, these factors must be recognized in any attempt to adjust test conditions for a bench test so that its results agree with the field test data.

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