I am having the same problem on my 89 300 se. I have 181K on mine. I have had the valve job done. Mine was using about a quart & a half on a 800 mile trip. Driving around town, it probably would not use more than a half every 1500 miles or so. I am taking mine back in to the shop on monday. According to Chiltons guide on oil in on the spark plugs, the problem is usually either valve seals or piston rings. I have had the seals/guides checked since the job was done and they seem ok. My guess is going to be piston rings. You would think in removing the heads and tearing everything down that a machine shop or the mechanic would check those, but my guess is that they did not and when putting everything back together, the problem continued to exist. If someone else knows more than this, please respond. I only know what I have experienced and read, which may or may not be much help. Scott