My 2005 Saturn Relay got a hole in a water hose and suddenly overheated, so I shut it down immediately. Found the crank case empty and the coolant full of oil. Replaced the hose and put oil in it, and fired it up. Runs as smoothly as ever but more oil getting into the coolant and the oil level dropping. Could there be an intake manifold problem like in old Buicks? 185000 miles on it but can't afford a new car, so how much to invest is a question.
sounds like the cylinder head became warped or cracked during the overheating. I'm not familiar with your car so it may be possible it's just the head gasket and not the actual head. Cylinder heads have "caverns" and ports to circulate coolant and oil throughout the head, but normally seperately. if they are mixing, something is very wrong. i would advise not running it anymore at all. the head and head gasket need to be inspected/repaired and cooling system flushed of oil, etc.