Every Chevy that I have owned used to use up that first 1/2 to full quart and then stay that low until the
oil change.
If it is not a torn/sucked up intake gasket you might want to pull the heads and have them checked for cracks.
Sounds like it could be a small crack in the head (hope not).
After the engine sets overnight, pull the plugs and get something like a q-tip (but longer) and stick it in the plug hole down to the piston. You can see just how much
oil is sitting and which cylinder is the bad guy.
Terry