Me.. 89 300SEL..150K.. I uesd to use about a quart of oil per 700 miles.. I have added oil stop leak for the past two oil changes, and my oil consumption has completely stopped.. It wasn't leaking, but I suspect the the valve stem seals were the problem. In any event, my problem has gone away for now anyway
Maybe I just had sticky rings from the previous owner's neglect??
May not be a long term solution, but it was a cheap, and easy patch, and oil is plentiful, and cheap..