I use Rotella in a lot of my diesel engines, Mobil 1 on the newer common rail engines, and I also add Zinc additive to help protect the cams and tappets in the engines. The zinc additives have been removed from diesel oils recently. I use either ZDDP or Lucas zinc plus. Tappet wear has dropped with running these additives. I've ran 15w40 Rotella in a few gas engines and had no ill issues either. I was actually planning on running it in my Hemi. I've heard the older engines have looser tolerances and will require a heavier oil to maintain proper pressure. I don't know how true that is, but it makes sense to me.