Too much ZDDP can cause corrosion inhibitors to become less effective. In general, you don't want to exceed more than 1800 ppm. This probably wouldn't be an issue for break-in, though. A while back, we tested several oils using neutron activation analysis to determine ZDDP content. We published the results, which can be downloaded here.
"When I'm in a slump, I comfort myself by saying if I believe in dinosaurs, then somewhere, they must be believing in me. And if they believe in me, then I can believe in me." - Mookie Wilson
