Read this thread, but only posts by Bbobynski. He is/was a GM engine designer. If we can't believe his advice, then we know more than the manufacture does and should not be posting on this forum in the first place.
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=129903&page=2
From posting 129881:
While the official answer is that the factory oil fill is nothing special....just plain 5W30 Mobil 1 just like you get in the store...the fact is that the engine was assembled on the assembly line with a small amount of ZDP rich assembly lube applied to critical surfaces as assembly lube. Cylinder walls, ring, ring lands, bearings, cam lobes, etc. all receive local applications of a Lubrizol assembly lube product an/or EOS. This assembly lube probably totals around 6 ounces or so total for the engine. This obviously protects against local scuffing or wear during the initial few seconds of operation and then the ZDP rich assembly lube is washed into the oil and contributes to spiking the factory oil fill with extra ZDP....so....in fact, the factory oil fill does, by default, have slightly higher levels of ZDP to guard against breakin wear. Removing this oil and changing early does put less ZDP in the oil for the breakin miles that follow.
It is probably not a big deal at all because the ZDP additive is fairly small, most of the purpose of it being in the oil is covered by the first few miles of operation and new oil would have a certain level of ZDP equivalent to the factory fill oil anyway assuming some of the extra ZDP was used up during the earliest moments of breakin.
But, the fact is that the factory oil fill is a bit "special" having that spike of ZDP rich assembly lube in it.
If you must change early for piece of mind, you could add a pint of GM EOS to the new oil fill to replicate the assembly lube addition to the factory oil fill.
Personally, I would just run the factory oil fill to the first change interval. If you do want to change early, follow the oil life monitor and change at 50% oil life or something like that for an early first change. Changing at 500 and 2000 is a waste of time and money as the oil in the engine at that point is perfectly fine. It won't hurt to change it, especially if you add the EOS but it really isn't going to help anything, either.
I have seen a lot of factory engines torn down after running lots of miles with the factory oil fill and they look perfect inside with no harm done whatsoever by running the oil to the first full oil monitor change interval.