As I had said, it was a visual inspection… But you can tell a lot about some things when you cut them open and look inside…
MY personal cutting open and looking inside was back in the 90’s…
The anti drain back valves (FRAM added/upgraded theirs in 2018) amount of filter element was about 2/3rd (less pleats, clogs faster then is by passed) of every other filter out there at the time, found rust inside of multiple FRAMS, no other brand including the better/best FRAMS had rust in them…
I have seen flow and other test also…
Here is one visual inspection of some filters out there, I have not found the video that showed the rust inside yet…
(I’m not buying and cutting a bunch open now a days), but I do always cut open my fun car oil filters just to look for any of the bad stuff… lol
Yes, FRAM has name recognition, but marketing is the reason for that… And back in the day they were almost always the cheapest on the market…
As far as I am concerned FRAM air filters are as good as the next guys, and the better/ best oil filters seem good…
And no, I have never seen an engine directly failed due to an oil filter (other than a flat out failure), but I have also never seen a controlled long term test for wear and tear on engines using different oil filters…