I own an '87 260E. Odometer shows approx. 145,000 miles. Dealer records indicate 26 oil changes, twice per year on average. Average distance between oil changes = 5,600 miles. No work has been done on the engine (i.e. still has the original valve stem guides and seals), and it has never seen synthetic oil. Oil consumption varies between 1 quart per 1,200 (highway) to 1,500 (city) miles. I wonder if religious oil changes and/or usage of synthetic oil would have made any difference. Also, should I expect oil consumption to increase rapidly, or gradually from now on? I have owned it for about six months and I change the oil every 3,792 miles (6,000 km).