Just some perspective - my 850 (1995) with 130K miles uses more oil than yours - no leaks, rebreathing system is clean, filler cap test passes, using 10W30 or 10W40 oil. Most of my 130K has been city driving which is relatively hard on a car. On previous cars which I used dominantly for highway driving, I have used 20w50 oil during warm seasons once they got over 150K miles or so. I can't imagine this oil giving problems vs 10W40 in an engine which is usually driven while thoroughly warm. I wouldn't use it in city/cold weather driving, for the reasons Klaus states, as well as hard to turn over and poorer fuel economy. Some mfrs specify a much lighter oil such as 5W30 - I would definitely not use 20W50 in such a car.

Could you have a seal leak which is not obvious - the oil may blow off the leak area while you are driving. If the block is not really dry of oil, oil must be coming from somewhere.