When did multi viscosity oils come out?

[Shannow]

You're welcome...I really liked that "thermal diffusion" bit.
Was almost like they had a thermal lab mechanism of separating "basestocks" by "viscosity index"...

Reminded me of Maxwell's Demon...vortex tubes...but obviously completely different.

 

[Oldmoparguy1]

I used 30W in my 65 GTO when I lived in California, later, when i moved back to Michigan, I used 10W-40 in everything. 3000 mile OCI of course.

 

[CR94]

Originally Posted by ZeeOSix
Originally Posted by zrxkawboy
I was surprised to see 5W20 shown on the viscosity chart in the FSM for my '57 Plymouth.
That is surprising, so the "thick vs thin" debates probably also started back then too.
Likely it was recommended only for winter use. My 1962 Chevrolet manual recommends straight 5W or 5W-20 only "when the lowest anticipated temperature during time oil will be in the crankcase" will be under 0°F.