I am not going to say that some or all of the suggestions posted to your original post could solve your problem. BUT, be careful and don't throw money in the wind. I have an 89 300se with 196k on it now. At about 175k(owned since 164k) I notice a significant amount of oil consumption. It was and still is using about a quart to quart and a half every 700-800 miles. I have replaced the oil cap gasket/seal. I talked to one of my mb mechanics and he said it probably needed a valve job with the mileage on it. So, I spent about $800 to have it done and immediately saw I had the same problem. My car now fouls cylinder 2 & 6 the worst, but about every 2 months, I have to put a new set of plugs in it. I have tried synthetic to help clean the system. It does the best with the synthetic, but the problem is still there. So, I basically threw $800 in the wind. My other mechanic says with it having a valve job done, it probably needs rings. I have read posts here that a valve job helped the problem and I don't doubt that a bit, but I want to warn you that it may not take care of your problem if yours is like mine. I hope I have been helpful.