For most of us on this forum it is likely more a matter of convenience than ensuring we get the last drop of old oil out. I use the suction device because it makes it too easy to change the oil timely, year round, to miss an oil change. Frequent, regular changes are more important than the intellectual argument over the last drop of oil in there if it has only been there for a couple thousand miles.

Using Delvac 1 for intervals of 6,000 miles I can drive the E300 TurboDiesel for up to about 150 miles before the oil turns black. I think I am getting most of the old oil out. 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)