Yep the oil is going somewhere, better figure it out before you have to replace the cat's. If it happend all of a sudden something broke, maybe a ring. If it was the valve steam seals it should smoke on start up, but they don't fail all of a sudden unless one came lose somehow.

My W124 M103 oil consumption got steadily worse over time to about 1 litre per 1,000-1,200 km. Replaced valve seals and consumption is 1 litre per 5,000 km. Job was done without removal of the head. Provided valve seals and valve cover gasket. Indy charged $300 CAD.

50 mpq? I had a F250 that I used to pick up parts cars that burned oil like that. Had to buy oil by the case when I went to pick up parts cars. At that rate you wouold definitely see blue smoke out the exhaust - or oil splash under the car,,, NO TWO WAYS about it! So where do you see the oil?

My concern would be if it happend all of a sudden, and it wasn't leaking. That means something broke, it could be an oil ring...