My '92 300e 2.6 was using about a quart every 500 miles. I replaced the valve stem seals and consumption went down to 1 quart in 2500 miles. I did the job myself, $10 for parts and didn't have to remove the head (used air compressor to hold valves in place).

My suggestion would be to try replacing the valve stem seals first, if that doesn't help, I would remove the head and have new valve guides installed.

-John