Originally Posted By: TrevorS
That large spacing must be taking more pressure due to the greater volume of oil that it holds. It can't flex as much at the end caps and gives way.
Maybe the filter medium is too restrictive and / or not strong / rigid enough.
I wonder if the Bosch Premiums are now 99% efficient because they are less restrictive.
Counter to that, have we seen Classics with this problem or only P1 and BPs?
The same pressure is acting on all surfaces of the media, it's just that when the pleat spacing is large, the pressure force can push the pleat over to try and flatten it, and that force causes the media to tear at the root of the pleat where it's glued to the end cap. You can take a filter and push the pleat sideways with your finger near the root and can hear the media tearing.
Media tearing is also seen on Purolator Classics. Purolators are not really that restrictive, but they do like every other filter in the world have some delta-p across the media.
http://www.bobistheoilguy.com/forums/ubb...451#Post1619451
And what's probably happening is that these media tears are happening in colder weather when the oil is cold and thick, and the filter goes near or into bypass, which means there is more like 12~16 PSI of delta-p acting on the media.