Having watched "The Motor Oil Geek" on Youtube a bunch, I've come to believe that the diesel formulated oils are best left to diesels. The reason is the high level of calcium that is used as a soot dispersant. That wouldn't be a problem except that it competes with ZDDP for the spaces in the metal pores, which is a problem on flat-tappet cams. I believe all the engines that spec the various API CK oils have roller lifters. I have run DELO in mine and after I didn't get it free anymore switched to Rotella T3. When I had the engine apart after 100,000 mi. to put that cam in another engine, I could tell there was some cam and lifter wear. Not enough wear to stop me from reusing the parts but I could see it. I am now using Castrol GTX classic with the high zinc additive package -- 20-50 in summer and now 10-40 for winter (goes below zero F here frequently).
