Tribology Letters

, 66:58 | Cite as

Review of Viscosity Modifier Lubricant Additives

  • Ashlie Martini
  • Uma Shantini Ramasamy
  • Michelle Len


This article reviews viscosity modifiers, additives that increase the viscosity of lubricating oils. Viscosity modifiers are high molecular weight polymers whose functionality is derived from their thickening efficiency, viscosity–temperature relationship, and shear stability. There are now many different additive chemistries and architectures available, all of which have advantages and disadvantages, and affect solution viscosity through different mechanisms. Understanding these mechanisms and how they impart additive function is critical to the development of new viscosity modifiers that enable lubricants to function more efficiently over a wide range of temperatures.


Viscosity modifiers Viscosity index improvers Lubricant additives 



We thank Michael Covitch and Joan Souchik for invaluable feedback on the manuscript, as well as David Gray, Hugh Spikes and Paul Michael for helpful input. We also acknowledge the Donors of the American Chemical Society Petroleum Research Fund (Grant #55026-ND6), National Science Foundation Engineering Research Center for Compact and Efficient Fluid Power EEC 05440834, and the National Fluid Power Association Education and Technology Foundations Pascal Society for support of this research.


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Authors and Affiliations

  1. 1.Department of Mechanical EngineeringUniversity of California MercedMercedUSA

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