JHZR2,

I use Delvac 1 and change it between 6,000 and 8,000 (longest interval yet) miles. When I first switched to Delvac 1 I changed it every 3,000 miles for a couple of cycles. I use the dipstick sucking tool. After a change to Delvac 1 I actually run for about a hundred miles and the oil is still clean! Changing it hot helps with this, but I also think the Delvac 1 really keeps the soot in suspension, so it drains out with the oil. Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)