Originally Posted By: goodtimes
Originally Posted By: ZeeOSix
Originally Posted By: shinyWheels
If the filter is upside down, couldn't the oil still drain through the middle hole on the filter? I believe that side is going to the engine, but over time wouldn't it seep through?
It seems like it should, but it doesn't. I think the surface tension of the oil is enough to prevent it from leaking through the media and out the center tube when sitting base down. I've let filters sit base end down for a week and the guts of the filter was still full of oil. But if you stick something in the base inlet holes to raise the ADBV off the base plate, then all the oil will drain out pretty easily.
Like described in this thread:
Link
If oil is poured into the center hole to prefill a filter, it fairly quickly passes through the media. There is air above the oil. Surface tension may play a part in keeping the vacuum lock,but it seems it would mainly be the vacuum causing the oils to stay put.
Agreed, it's really both the surface tension and the vacuum created inside the closed volume. That's why I punch a hole in the top of the filter's dome on filters that are mounted vertically with the base down. Punching a hole in the dome enables the filter to drain completely before removal.