Lubrecon - I disagree. It depends on the rings you are using on the break in of a fresh engine and the clearances you use. If you are using molly rings you are right, you can use synthetics most times though. A couple of years back I built a "tight" engine using stock iron parts and broke it in with Moble1 and it broke in so funny(weird) that I tore it apart after 700 miles to see what was going on. (it had blowby and compression issues) Nothing wrong, I put it back with 20w straight weight mineral
oil. After about 30 mins. of use later it started to come around. As for the type of
oil to use after a break in, I usially tell most folks with street cars like Cobras that Red Line followed by Moble1 is the way to go. I'm a drag racer so I use Royal Purple of course. With a new "loose" drag motor you can almost use anything you have sitting around to my way of thinking though. As for ZDDP, the more stuff you throw into
oil the yukkier the oil change is when that stuff wears out. With less stuff in there the more you have to change the oil, like what the manufacturer recomends- imagine that! Motorcycles have wet clutches a lot of times and I think thats the logic there of more friction additives because a lot of times M/C manufacturers tell you NOT to run synthetics because of wet clutches. In fact I knew of one bike a couple of years ago that synthetics would void the warranty, and I'm not a bike guy.
cobrashock