With a new motor thats not so uncommon. Often there are no signs of "smoke", the plugs are clean and nice, everything is fine. Rings and what not just haven't fully seated yet is my guess. Any signs of
oil under the car on the pan or around the back of the engine? Even a VERY small leak over time will drop enough
oil to go low.
Like a SLIGHT leak around the
oil pan drain plug will leak out a couple of quarts within a few weeks. Those tiny leaks can be deceiving in how much oil they will loose.