I would ask when was the last time the valve cover seal was replaced. A bad one will leak like a sieve, but not 1 qt/500 miles, maybe 1 qt/1k is possible. They can leak bad enough to produce oil vapors at stop lights and a steady burning oil smell.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.