Unsourced material may be challenged and removed. The best oils with the highest VI will remain stable and not vary much in viscosity over the temperature range. Retrieved from " https: From Wikipedia, the free encyclopedia. This article needs additional citations for verification.
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Lubricant Storage and Handling. VI improving additives and higher quality base oils are widely used nowadays which increase the VIs attainable beyond the value of The more variable the conditions, the greater the need for high VI oils. Unsourced material may be challenged and removed. Lubricants Oil additives Tribology.
Can an Oil's Viscosity be Reduced? Current Issue Archive Advertise.
The best oils with the highest VI will remain stable and not vary much in viscosity over the temperature range. Comparing the d2270 VI oil to the VI oil, there is a percent difference in viscosity at minus 20 degrees C and a minus percent difference at degrees C.
This too calls for a high VI lubricant. Views Read Edit View history. Toggle navigation Toggle search. Retrieved 29 August If the lubricant is too viscous, it will require a large amount of energy to move as in honey ; if it is too thin, the surfaces will come in contact and friction will increase.
Outdoor mobile equipment typically works under these challenging conditions.
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Possible Causes of Thickening Gear Oil. However, the vast majority of lubricants on the market will have VIs in the range of 90 to This is shown in the table below.
We all know that viscosity is the single most important physical property of a lubricant. The VI was originally measured on a scale from 0 to ; however, advancements in lubrication science have led to the development of oils with much higher VIs. The Viscosity Index of synthetic oils ranges from 80 to over These conditions influence temperature, which in turn influences viscosity, which influences the protection provided. How to Cost Justify a Lubrication Program.
ASTM D - Viscosity Index (VI) Calculator
Certain additives, such as viscosity-index improvers and pour-point depressants, influence VI as well. May Learn how and when to remove this template message. This simple number is there for a reason and should be strongly considered when writing a specification for lubricants in nearly all machine applications. Generally, the least viscous lubricant which still forces the two moving surfaces apart to achieve " fluid bearing " conditions is desired.
This article needs additional citations for verification. You can use these calculators in a variety of ways.
Don't Ignore Viscosity Index When Selecting a Lubricant
For instance, if you know the viscosity of a lubricant at two different temperatures, you can use the calculator to give you an estimation of the VI. Since the inception of the scale better oils have also been produced, leading to VIs greater than see below. Based on the methodology, Pennsylvania crude d220 was set as a benchmark at one extreme, representing low viscosity changeability relative to temperature.