zinc oil useage?

92b.
Yes correct about the levels of zinc. When you look at different oils that have zinc, the amount varies greatly, often from 800 ppm to over 2000 ppm. That tells any sensible person that more zinc is adding for marketing purposes [ ' Buy ours, it has more zinc' ]....or nobody really knows for sure if there is a defined/minimum amount that is needed & any more than that is wasted.

A dyno test with, say, 1000 ppm of zinc in the oil, & the same oil without the zinc will prove whether zinc is a 'power eater'. It is no different from a claim that thicker oils costs hp.
You dyno test the same brand/type of oil in high & low viscosities...& let the dyno tell the story.