Thanks.

One thing to remember with API ratings is a SG/SJ vs. the newer SM or better yet the ILSAC ratings is the limiting of Zinc, Phosphorous, etc. Our car's CAT converters don't like all those good things that protect the engine.

Some gas engines do better with the diesel rated oil in them...

I've always been told that for our boat engines, your want the most Zinc, Phos, etc. because that is the protection in the oils. That's why using a SM rated oil would not be smart for the boat engines.

One thing that would be interesting is what Merc and VP recommend in the new CAT engines ???

The Supertech Synthetic I have in my truck now is SM, and the Rotella I'm about to toss in the boat is SL. I'd use Rotella in my truck, but it calls for 5W30, and newer Hemi's use 5W20 because of the MDS system.