Originally Posted by
ThermionicScott
A tangent, sorry: W does
*not* stand for "weight", even though it was common to refer to grades of oil that way! It's a measure of the oil's ability to flow at cold temperatures ("W" = "winter".) For instance, a 10W30 oil or 80W90 transmission oil has to be able to flow at -25°C or it doesn't get that "W" number. The higher number has to do with its viscosity at hot temperatures, originally 100°C although a 150°C spec was added a few decades ago.
Bicycling-friendly temperatures are somewhere in the middle of those two ratings, so we needn't worry too much about the exact numbers.
Of course "
Winter" makes total sense. I wanted to make my description easy to understand... but...
I retired last year after a 40 year career in manufacturing, engineering, and industrial sales in the metal working industry. For almost 10 years before that I was involved at least monthly with the machine shop at Chevron's Research Facility in Richmond, CA.
One of the labs responsibilities was continually running QC friction tests on their existing lubrication products as well as experiments on new high pressure additives and new types of lubricants. The gold standard was to run 2 hardened rotating small steel wheels or disks against each other under controlled pressure until failure to measure a lubricant's longevity and breakdown characteristics.
Even the folks at the lab referred to "
W" as "
Weight" when discussing viscosity.
While working my way through school in the 60's and 70's I wrenched on everything from VWs to steel mill machinery (and finally bicycles).
xx
Weight was always the
vernacular used to specify the viscosity of liquid petroleum based lubricants - from 5W and 10W transmission fluids (
ATF) to 120W and heavier gear oils...
It's like Kleenex and other vernacular terms that have become part of the language....
BTW, lubricants used in jet aircraft engines are some of the most challenging applications because they have to withstand extremely high temperatures as well as extremely low temperatures at higher altitudes.
verktyg
