Viscosity determination in sight glass tube

[safspir]

Now here's a possibly funny one. Today we were discussing the relative merits of having sight glass tubes versus using magnetic and other types of sensors. I kind of "off the cuff", related how an old ships engineer had once told me he could tell the viscosity of an oil by reading it's meniscus in a sight glass tube. Of course, the other guys asked what drugs I was on, and whether I had indulged in lead paint chips as a child. I really hadn't given it much thought until today, had kind of written it off to "old man brain". But now, "that I are one", and having done some web research, I'm wondering is maybe he didn't have some kind of point. Okay, any takers?

 

[prex]

Capillary action has nothing to do with viscosity.

prex
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[bimr]

The meniscus is the curve caused by surface tension in the upper surface of a liquid. Surface tension changes with temperature.

Viscosity is determined by the time it takes a given amount of liquid to flow through an instrument called a viscometer tube; essentially a narrow pipe. Viscosity also changes with temperature.

I don't think that there is a correlation between surface tension and viscosity. An explanation is that surface tension is correlated to steady state and viscosity is correlated to movement.

Perhaps the old ship engineer was shaking the sight tube?