> With this recent discussion of gear oil and shock oils, it is important to
> point out that (if I'm not mistaken) there are completely different
> standards for reporting gear oil and engine oil weights. On
> engine oil, the upper number is based on the viscosity at 212 degrees F.
Maybe
> someone can clarify this, but I believe gear oil goes by a completely
different
> standard.
It is indeed a completely different scale.
http://www.micapeak.com/info/oiled.html
has a simple chart that I like, it makes clear the relationship between gear
oil and motor oil. However, the other numbers on that page may or may not
reflect today's reality, some of them haven't been updated for 10 years or
more. Surprise, surprise, motor oils are very prone to "change without
notice".
> and I have no idea about hydraulic shock oil.
I'm not sure, but I think they use yet a third scale, known as the ASTM
(American Society for Testing and Measurement) scale. AMSOIL "Shock Therapy
Light" is described as a 5 weight shock oil, but the spec says 4.38 cSt @
100C, which puts it solidly in the 10 weight bin for motor oil. STM is
described as 10 weight, but the spec says 7.33 cSt @ 100C, which would be a
20 weight motor oil. However, these match pretty well with the ASTM scale
(which is basically just the cSt @ 40C)
http://www.amsoil.com/products/stl.html
However, the AMSOIL site says no standard exists ... <g>
Randall
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