'92 300e

I am at the point to make effort to stop the oil loss on the MB. After having it for 4K miles now...it goes thru a quart of oil in approx. 700 miles. Testing after a complete oil change. It does not leak any oil on the ground or leave anything more than a slight trace on the under pan. Nothing like 4 quarts that have been lost in less than 3 thousand miles since I changed oil. The plugs don't show oily like my 190E did that the quides were worn out in. It doesn't appear to smoke any either. I was wondering if there was anything I should check possibly for the problem before I tear the top end down? The car has 90K on it, and has had the oil & filter changed in a mercedes dealership every 3 thousand miles. I, also, would like to know if it is guide problems in this car also...if there are any better ones I can get to use than factory ones. I wouldn't want to have to redo this again, if in fact that is the problem. Any help or advice that you can offer would be appreciated. Thanks, Rebe