Originally Posted By: wannafbody
I always assumed that the oil just drained out through the center tube. I had read that a filter won't completely drain and I wanted to check and see if that was really true.
Kind of reminds me of the "trick" used on oil filters that are mounted with the base down/top up (ie, RX-7s, 05+ Tacomas) to prevent a mess during an oil change. Punch a hole in the top of the filter and let the filter drain over night. When the filter is removed, there was zero oil mess ... whereas if you just drained the oil pan and then removed the filter 10 minutes later it would puke oil all over the place.
In a case like that, the oil is trapped in the filter due to the anti-drain back valve and the vacuum factor. Put a straw in a glass of water, cover the end with your finger, remove the straw from the glass and you will see a column of water remains in the straw. Remove your finger from the end of the straw and the water falls out.