Volvo: Oil blow by in 940 with 200k miles, oil filler cap, flame trap

Question
What could be the cause of blow by at oil filler cap with new cap seal and new flame trap.  I seem to be using or loosing about 1 qt ever 500 miles on the road at 80mph around town not so bad.  Rear main seal is starting to leak.  Could it be oil rings? or turbo seals turbo is original

Answer
Henry,
Run a cylinder leakage test that will let you know about the rings. Take a compression test also to see if you have a weak cylinder. There is not a way to know how much oil is lost while driving unless you check it before your road trip and after. That could also mean loose of oil from bad rings or guides. Some testing will need to take place to determine where the loss is at. Maybe fix the rear main and see how that works.