viscosity index

noun

: 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

Example Sentences

Recent Examples on the Web An oil’s resistance to thinning in hotter temperatures is called the viscosity index. —

Paul Weissler, Popular Mechanics, 31 Aug. 2020 Resistance to thinning with increasing temperature is called viscosity index. —

Paul Weissler, Popular Mechanics, 14 Feb. 2019 Resistance to thinning with increasing temperature is called viscosity index. —

Paul Weissler, Popular Mechanics, 14 Feb. 2019 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'viscosity index.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History

First Known Use

1929, in the meaning defined above

Time Traveler

The first known use of viscosity index was in 1929

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Dictionary Entries Near viscosity index

viscosity breaking

viscosity index

viscount

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Cite this Entry

Style

“Viscosity index.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/viscosity%20index. Accessed 22 Mar. 2023.

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