With all the threads and web pages I've looked at. (Pause and face palm)
I did not know this.
IIRC someone gave a link to a web site that supposedly had zinc listing for oils by brand.
I discounted that because I assumed oil manufactures change things over time.
What you have said about Mobil 1 surprises me since
1. I believe some new cars specify synthetic oil. (I really don't keep up with that.)
2. It was my understanding that zinc has been taken out of oils intended for new cars because of catalytic converters.
Therefore, it does surprise me that any oil intended for new car has zinc it.
Now, that being said, I'm glad to hear it.
I've been running Mobil 1 for 15 years in an daily driven 86 318 with no trouble.
And only in the last few years I've started adding STP just to be "safe" because it has zinc in it.
Here's what I think.
Only high lift cams might cause problems.
Us people with mushy factory cams probably don't have much to worry about.