I have changed my oil a few times and usually fill to top install plug unscrew pump and replace drain plug. I have read on here to let 2 oz drain before installing drain plug. My owners manual does not say that, is states fill to top and replace drain plug as fast as poss. I was taught that air in a non-vented system will compress and build pressure if left in. That is why to fill void completely. Just wondering.
THX