ASTM_DS49-1973.pdf

SHEAR STABILITY OF MULTIGRADE CRANKCASE OIL Establishment of Field Data and Correlation with Laboratory Engine and Bench Test Results Prepared by the Data Analysis Panel of ASTM Committee D-2 Research and Development Division VII B-1 on the Shear Stability of Crankcase Oils ASTM DATA SERIES PUBLICATION DS 49 List price$7.75 05-049000-12 AMERICAN SOCIETY FOR TESTING AND MATERIALS ANNiVEtsARr 1916 Race Street,Philadelphia,Pa.19103 by American Society for Testing and Materials 1973 Library of Congress Catalog Card Number:73-78863 NOTE The Society is not responsible,as a body,for the statements and opinions advanced in this publication.Printed in New Carlisle,Ohio June 1973 -1-I.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 refer-ence 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(ARC*-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 influ-enced 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.II.INTRODUCTION AND BACKGROUND Evaluation of the viscosity stability of multigrade oils has been a major concern of Section B of ASTM R&D Div.VII since its organiza-tion in 1952.In 1955,six participants ran tests on two hydraulic fluids formulated with two different molecular weight V.I.improvers of the same chemical type(polyalkylmethacrylates).Techniques evaluated at that time included sonic(magnetostrictive)oscillators,pumps with sharp-edged orifices or pressure release valves,and a diesel fuel injector.On plot-ting percent viscosity loss of one reference fluid against percent viscosity loss of the other reference fluid under identical test conditions,members of the section found that data points from most of the shear methods studied fell reasonable well on a single curve.They therefore concluded(1)*that the various shear methods gave equivalent results under conditions of identical severity.In 1957,R&D Div.VIIB conducted a cooperative program in which 12 laboratories evaluated a sonic oscillator method.This program led to a publication in 1961(2)of a method for measuring the sonic shear stability of polymer-containing oils.The three reference oils used in this program were each prepared by adding sufficient V.I.improver to a 150 neutral base oil to double its viscosity at 100 F.Three different chemical types of V.I.improvers were selected for the program without regard for molecular weight and consequent shear stability.The sonic method,though somewhat lacking in precision and having unknown correlation with field performance,was published for information because it promised to be a useful tool for monitoring lot-to-lot variations in the manufacture of a given polymer con-centrate or blend.While the simplicity and rapidity of the sonic Numbers in parentheses designate References at end of paper.DS49-EB/Jun.1973Copyright 1973 by ASTM International www.astm.org-2-shear method have appeal,attempts to extend its use to different chemical types of V.I.improvers have met with difficulties(3).For lack of a better method,R&D Div.VIIB voted in 1966 to republish the sonic method as a tentative(4)despite the evidence of poor correlation with tests designed to simulate specific service conditions.In 1967,a new Subsection,B-l,was formed to study ways of evaluating the shear stability of polymer-containing oils under conditions closely related to service.The Subsection circulated a questionnaire to representatives of industry,government and research organizations to find out what methods were being used for the measurement of shear stability.Response to the questionnaire led to the decision to obtain field data on a representative set of fully formulated multigrade crankcase oils contain-ing all of the V.I.improver chemical types then available or likely to be available in the near future.These data would then be used by the Subsection to judge the relative merits of various laborat