RRSBighorn
Active Member
Here's two pictures - 10-48 Royal Purple Filter - Purple Silicon looks like its folded over itself...
The other filter was a new filter but not the one that I put in and look how nice that orange silicone is seated...
Thought that was interesting to share...
Those pictures got me to thinking. I worked in the oil industry for 40+ years and worked in engineering. We had to deal with elastomer chemical compatibility issues on a regular basis. The anti drainback valve is one piece but it has a larger o-ring part built in that seals around the outside of the center internal threaded hole. The rest of the integrated valve is basically like a flat circular flap (see attachment) that seals against the bottom of the filter housing preventing the housing from draining back when vehicle is not running. It is basically a check valve allowing oil flow in through the 6 or 7 small holes around the outside of the filter element with clean oil coming out the center.
I forgot that silicone is typically not a recommended elastomer for petroleum oil and gasoline (see attachment). The Purple oil and Amsoil filters both say they have silicone drainback valves. There are many mixed compounds, so you will get different compatibility ratings with from different manufacturers. But looking at the Purple Filter, the o-ring part looks swollen, this is just one of the things that can happen to an elastomer that's not compatible with some chemicals. Also over time and at elevated temperatures, the elastomer can get hard. So one theory could be that a swollen or hard drainback valve could be limiting oil into filter housing, thus also looking like a plugged filter element and seeing lower pressure downstream.
I'm sure the oil filter engineers must of looked at this, but maybe they overlooked oil contamination, like excess fuel, or acid build-up in oil. My guess is Nitrile is used in other filter drainback valves, this is very compatible with petroleum products. I doubt it's that simple, but who knows, I don't know if a manufacturer would even admit it if that was the problem.
See attachments for reference.