The place I used to work for had 35K PMIs.
They used regular Chevron 10-30, not a 15-40 diesel oil like Rotella or Delvac.
Most went 1.4-1.5M before they sold them off. Maybe 1 in 25 needed a "infame" before it reached the 1.5M goal.

I use regular 10-30, brand is determined by current lowest price. I add a bottle of ZDDPlus like Y07 posted above, only because I have a supply of it. Once it's gone, I'm going with one of the oils with correct Z-P in it.