Peter,

Last I heard most dealers use suction devices to pull oil from the cranks - saves time, is cleaner and has been shown to remove as much oil as draining from the drain plug.

Do a search - several folks have use the suction devices (several different kinds) measured the oil, removed the plug, etc and find that suction works very well, indeed - leaving almost nothing. In my opinion, even if you left 1/2 quart in the pan, and add 8 more, and then do the same in 10K miles, and then repeat for 300K miles - it likely will be meaningless. Not perfect, but not enough to cause damage.

__________________
George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg