If you have not already, you might want to go over to
540 Rat's Motor Oil Test Data site. The blog is huge, somewhere around 390 pages if you download it — but quite good.
If you search the site for
Zinc you will find some quite interesting information with the just the first two hits (not to mention all the others). Additionally if you search
WEAR PROTECTION RANKING LIST he ranks the oils by film strength from highest to lowest. One of the interesting items is the effect of the commercial additive
Prolong.
I think you will find the work he has done quite interesting and equally useful. Additionally if your print driver allows, you can print the entire blog to your hard disk as a searchable PDF file.
Hope this helps.
Ed