On the oil filters, you're talking about,
I think the plastic insert that fits between the filter end cap and base plate helps keep the filter element stay straight and snug.
Hi ZeeOsix,
Thanks for posting their new numbers, I haven't been to their site in a while.
I can remember just last fall the numbers were 99+% at 20 microns and the filter was good for 15,000 miles, funny how they change the numbers that way. At least Walmart's Supertech added a silicone...
A recent test shows the Pennzoil Platinum 5w20 has a Nowack of 8.2
https://pqia.org/pennzoil-platinum-full-synthetic-sae-5w-20-motor-oil/
And the Cam2 Super Pro Max Synthetic Blend 5w20 has a Nowack of 14.
https://pqia.org/cam2-super-pro-max-synthetic-blend-sae-5w-20-motor-oil/
I can tell you the ST3614 you have pictured has felt end caps and has a nitrile rubber anti-drain-back valve that also doubles as a bypass valve. That base plate design on the Supertech oil filters usually indicates that it has felt end caps.
To me JMHO, the only purpose it looks to serve is to...