The Engineering Society =For Advancing Mobility and Sea Air and Space, INTERNATIONAL- 400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096-0001 U.S.A. Formulating AutomaticTransmission Fluids with Improved Low Temperature Fluidity R.F. Watts J.P. Szykowski PARAMINS Exxon Chemical Company Linden, New Jersey International Fuels and Lubricants Meeting and Exposition Tulsa, Oklahoma October 22-25,1990 Downloaded from SAE International by University of Birmingham, Sunday, August 19, 2018The appearance of the ISSN code at the bottom of this page indicates SAE's consent that copies of the paper may be made for personal or internal use of specific clients. This consent is glven on the condition, however, that the copier pay a $5.00 per article copy fee through the Copyright Clearance Center, Inc., Operations Center, 27 Congress St., Salem, MA 01 970 for copying beyond that permitted by Sections 107or 1080f the U.S. Copyright Law. This consent does not extend to other kinds of copying such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale. SAE routinely stocks printed papers for a period of three years following date of publication. Direct your orders to SAE Customer Service Department. To obtain quantity reprint rates, permission to reprint a technical paper or permission to use copyrighted SAE publications in other works, contact the SAE Publications Group. Global OMabiity lDa.&hseB AM SAE papers are absrracred and mdsxed in the SAE Global Mobrl~ly Database No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior writ- ten permission of the publisher. ISSN 01 48-71 91 Copyright 1990 Society of Automotive Engineers, Inc. Positions and opinions advanced in this paper are those of the Persons wishing to submit papers to be considered for presen- author(s) and not necessarily thoseof SAE. Theauthor issoleiy tation or publication through SAE should send the manuscript responsible for the content of the paper. A process is available or a300 word abstract of aproposed manuscript to: Secretary, by which discussions will be printed with the paper if it is Engineering Activity Board, SAE. published in SAE Transactions. For permission to publish this paper in full or in part, contact the SAE Publications Division. Printed in USA Downloaded from SAE International by University of Birmingham, Sunday, August 19, 2018Formulating AutomaticTransmission Fluids with Improved Low Temperature Fluidity R.F. Watts J.P. Szykowski PARAMINS Exxon Chemical Company Linden, New Jersey ABSTRACT The driving force for reducing the low- temperature viscosity of automatic transmission fluids is improving low temperature transmission operability. The need for this change in fluid performance can be attributed to the evolution from hydraulic control of transmissions to elec- tronic control. This new requirement for auto- matic transmission fluids of improved low tem- perature fluidity causes a shift in the viscosity of the base oil used to blend the fluid. Conventional mineral oils are still acceptable bases for these new fluids as well as specially refined mineral oils and synthetics. The shift in fluid rheology and base oils also impacts oxidation resistance, foam- ing characteristics, anti-wear performance in hydrodynamic regimes and fluid flash point. All of these potential problemscan be overcome by the correct choice of base fluids and additives. - Automatic transmission fluid (ATF) rheol- ogical properties affect transmission operation in three ways. The first is the change in fluid vis- cosity with temperature; the second, the change in fluid viscosity with miles (shear stability); and third, restricted operation at low temperatures due to poor pumpability or sluggish flow (1,2). The basic ATF viscometrics used today are derived from the DEXRO