Is temp vs vis always linear?

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263
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DFW, TX
I mean linear on a log scale. If I plot some different oils based on their 40*C and 100*C points given in the spec sheet, can I depend on this to be pretty accurate?
 
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901
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Northern Illinois
I don't see how they could be since multi-vis oils are non-newtonian fluids (I think) with different amounts of VPs and different distances between the low and high temp viscosities.
 

MolaKule

Staff member
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Iowegia - USA
If you plot on a graph the horizontal axis being a linear temperature scale, and the vertical axis being (either dynamic or kinematic) viscosity on a logarithmic scale, the curves of all oils are approximately second order with a negative slope.
 
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8,937
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SC
quote:
Originally posted by MolaKule: If you plot on a graph the horizontal axis being a linear temperature scale, and the vertical axis being (either dynamic or kinematic) viscosity on a logarithmic scale, the curves of all oils are approximately second order with a negative slope.
In other words, the plot appears linear on a graph such as the Mobil vta018a.pdf that Jay was kind enough to send me, but because the vertical axis is a log scale, actual viscosity change due to temp is not linear.
 
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