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
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An oil’s resistance to thinning in hotter temperatures is called the viscosity index.
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Paul Weissler, Popular Mechanics, 31 Aug. 2020
Resistance to thinning with increasing temperature is called viscosity index.
—Paul Weissler, Popular Mechanics, 14 Feb. 2019
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Paul Weissler, Popular Mechanics, 31 Aug. 2020
Resistance to thinning with increasing temperature is called viscosity index.
—Paul Weissler, Popular Mechanics, 14 Feb. 2019
Cite this Entry
“Viscosity index.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/viscosity%20index. Accessed 1 May. 2025.
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