I'm interested in getting one of these, I know how they work. My question, does all the oil get drained out, as well as a traditional drain bolt? The threaded stud that goes into the oil pan has to leave some oil in the pan. I just recently changed our oil, after the free 1st change, and found the bolt almost completely rounded off. I mentioned this to our service manager, who said bring it in so they could look at it. (LOL) I also witnessed a "mechanic" drop a mounted tire with a aluminum wheel from about 4 foot off the ground doing a tire rotation while changing oil! Needless to say I didn't find that funny at all!!!