Is temp vs vis always linear?

[Chris A]

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?

 

[dickwells]

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]

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.

 

[G-MAN]

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.

 

[MolaKule]

Correct!