We have found out that the Brad Penn oils they have lower zinc and phosephate for some reason and we have used this oil for cam break in for years with no probems and we also used the old Rotella T 15/40 before they lowed the zinc in that oil. In fact if you call Brad Penn thay won't even tell you the zinc content.
Now we have gone to the
http://www.cen-pe-co.com/ as they have a 15/40 for the older deisel engines that has 1582 ppm of zinc and over 1300 phosephate and they 20/50 oil is higher in both zinc and phosephate.