Originally Posted By: goodtimes
Now that I think about it there is the well known and observed fact oil filters can be prefilled. If it was surface tension preventing oil from passing through the media, it works both directions. It also depends on oil viscosity and temperature, but there is no doubt oil flows through the media only by gravity. So maybe I am not so mistaken as charged, and the gurus here are still just guys figuring things out like everyone else. Maybe it is air lock holding the oil inside, but it is not surface tension.
I think it's some of both ... read on.
The only difference is when the oil is trapped inside the filter, and tries to flow outward through the center tube, there seems to be some kind of slight vacuum or such ("air lock" as you call it) induced that also helps hold the oil inside the filter. One example is on an oil filter that is mounted on the engine vertically with base down (ie, Tacoma, RX-7s, etc). If you punch a hole in the top of the filter can it will drain the guts of the filter, but if you don't it will puke oil all over the place when unscrewed. Kind of like how you can hold fluid inside a straw if you put your finger over the end and then remove it from the drink. The fluid won't drain from the straw until you let your finger off the end (ie, opens it to atmosphere).
All I know is the experiment I did proved that even off the car they will hold all the oil inside the can if the ADBV seals 100%.
Now that I think about it there is the well known and observed fact oil filters can be prefilled. If it was surface tension preventing oil from passing through the media, it works both directions. It also depends on oil viscosity and temperature, but there is no doubt oil flows through the media only by gravity. So maybe I am not so mistaken as charged, and the gurus here are still just guys figuring things out like everyone else. Maybe it is air lock holding the oil inside, but it is not surface tension.
I think it's some of both ... read on.
The only difference is when the oil is trapped inside the filter, and tries to flow outward through the center tube, there seems to be some kind of slight vacuum or such ("air lock" as you call it) induced that also helps hold the oil inside the filter. One example is on an oil filter that is mounted on the engine vertically with base down (ie, Tacoma, RX-7s, etc). If you punch a hole in the top of the filter can it will drain the guts of the filter, but if you don't it will puke oil all over the place when unscrewed. Kind of like how you can hold fluid inside a straw if you put your finger over the end and then remove it from the drink. The fluid won't drain from the straw until you let your finger off the end (ie, opens it to atmosphere).
All I know is the experiment I did proved that even off the car they will hold all the oil inside the can if the ADBV seals 100%.