Causes of High Oil Consumption besides rings?
 

I rebuilt my 83 240 D motor two years ago. In the beginning oil consumption was none existent, but lately I 've been adding a quart every gas tank--sometimes much more!
I made the mistake of using non-Mercedes OEM rings and also not doing a rebore, but could this high an oil usage be due to that alone? Its as if oil is being "sucked" out of the Oil Pan or forced out. The exhaust is clean and the tailpipe is dry.
Are there any other reasons for High Oil Consumption, such as high Crankcase pressure, or fuel pump timing, anything at all?
Or are my worst fears being realized? At this rate, next year I wil be adding maybe 2 quarts oil a tank of gas.
Please help.

I agree with black mercedes If its not leaking its rings or valve guides .if its the rings I think that you would see blue smoke while its running if not ,check to see if it smokes after the car sits for a while like overnight and watch when you start it if theres any puff of blue smoke then its valve seals

When I rebuilt the engine, I had the head Redone with 4 of the sodium vaves replaced. The car doesnt burn smoke at all, and its performance is very good, starts great on first keystroke. I never see oil where its parked and the bottom is dry as a bone.

Thats why I am so puzzled. I can only think its the rings, but I see no smoke. What kind of test do I need?

Another long shot is the crank vent. Depending on its design it may suck oil that way.

When rebuilding a 240, we always did a resleeve and new rings.

The Crank Vent..
 

actually, I am thinking of this. I never did get my Vacuum Hose routing correct after the rebuild. Actually when I bought the car it was messed up, the doors didnt lock right and the trunk didnt lock right either...so I am going to take a shot in this direction this weekend. Thank you

I am having a similar problem. High oil consumption, but no smoke. I check at start up, I watch at idle and I have even had the wife drive up and down the road and I have seen no smoke. There is not a drop on the garage floor.

Jim Anderson mentioned the crank vent. Can you elaborate on this. In the winter I sometimes get a sludge build up, which I understand is moisture not burned off, and primarily caused by improper crankcase ventilation. I really have no understanding on this subject. Can this cause high oil consumption too? Car is '86 420SEL

Thanks