My mom and dad have a ML320, and they were told that draining the oil via the drain plug was bad news, because the M112 motor drain plug spits oil on the control arm bushings. MB has told it's dealers to suck the oil out because of this. The average shop/oil change place is NOT going to be aware of this. The MB indy my dad used sure didn't know, and pops likes to change his oil every 3k. It's a good thing they only did it two or three times.