I never could find the magazine article online about IH lubricants but I did find a link to the manufacturer. Trying to research this just led to countless online conversations/arguments.
I did find the specs for Case-IH low ash oil from the manufacturer (Viscosity Oil)
http://www.viscosityoil.com/pdf/P1_12.PDF
scroll down to page 1E10
appears to be .5% ash content
As far as I know this company has always made Hy-Tran for IH