Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Scrabble
  • Spanish Central
  • Learner's Dictionary

viscosity index


Definition of viscosity index

  1. :  an arbitrary number assigned as a measure of the constancy of the viscosity of a lubricating oil with change of temperature with higher numbers indicating viscosities that change little with temperature


First Known Use of viscosity index


Learn More about viscosity index

Seen and Heard

What made you want to look up viscosity index? Please tell us where you read or heard it (including the quote, if possible).