I've recently been doing some research on what's in the various brands of "break in" oil and am having a bit of trouble getting past the hype and into the facts myself. I suspect some of them have been blended by their Marketing Departments, not their Engineering Team...

FWIW, I'll be doing the initial start-up of my rebuilt 452 roller engine w/ Brad Penn's 30-wt break-in oil, but I don't plan on keeping it in for long. They've got a "tech paper" (wrapped in advertising?) on their web site that claims there are still ring-seating benefits to using it, and that the oils w/ the mega-high amounts of zinc & phos. are actually counter-productive to helping new rings seal.

Not much else I can offer at this time. I've asked the same basic question before and didn't get much fact-based input, either