Paul........you do know that the 9N was originally designed for 30wt DETERGENT oil, don't you??? Ford also recommended 40wt DETERGENT oil while working in HOT climate.
You do know that oil THINS when it gitts HOT, don't you??? That is called viscosity factor. No matter how good yer oilpump is, it can NOT make high pressure outta thin oil.
I don't like 10-30wt oil as it is THIN 10wt oil with temperature sensitive additives. Me? I use 20-50wt detergent oil.
Iff'n yer low HOT temperature oil pressure bothers you, change to 50wt RACING oil. (and filter) Simple, eh? .........oily Dell