That OEMs break in an engine with synthetic is sort of irrelevent to break-in of engines in general. Well it shows that if you are using the same rings and honing and whatever synthetics break-in fine. but there are people who know a lot about engines an oil and they say certain rings don't break-in as well with synthetic. I think it's moly rings or something like that. I don't know if the issues is slipperiness or synthetics oil the rings too good, or what.
I don't think breaking in with synthetics is usually an issue, but I don't really see the point either. OEMs have everything accounted for and they may use certain additives, and some suggest going the full OCI on the break-in oil. I'm more of the school of using a conventional and changing it early for break-in.
