My 89 560sel runs great but has consistently been increasingly using more and more oil. I religiously change oil every 1,500 miles however the engine is up to 1 quart every 250-300 miles. The car has 214,000 miles. The engine may need a rebuild however I have been told that it may be just the valves blowing by oil. I checked the compression and all cylinders are at about 175 psi and each are within 5 psi of each other. Is there a way I can check to see if it is valves? Thanks in advance! I love this forum.