Originally Posted By madscientist
... viscosity grades are a mile wide.

Yep. I have this chart in hard copy at home to compare different brands of "same weight" oils:



I've always thought the ranges across grades were highly inconsistent and came up w/ my own scale for comparison that IMO better equalizes the ranges across the viscosities. But it's just something I did 'cuz I wanted to, not that it's any true scientific tool for comparison.