Oil changes with rebuilt engine

[Bob Culver]

ACL, the major manufacturers of rings in Australasia, and who probably provided the new car industry when it existed, recommend for conventional cars that the first oil change be "as soon as possible and certainly before 500km". Presumably the iron dust, honing remnants, and workshop dust, grinder spray etc finds its way through the filter sooner or later.
(Incidentally hard drives contain very powerful flat magnets.)
From what I have read it seems a thermostat would likely have more effect on cyl wear than the difference between cheap and expensive oil or frequent changes