What worries me with the current Thailand-made Toyota/Denso oil filters (90915-YZZF1, 90915-YZZF2, etc.) is that I don't see much dirt captured in the media. This observation along with the Amsoil's test that puts the Thailand-made Toyota/Denso deep at the very bottom of the efficiency ratings makes me wonder if they actually do much filtration or leave most of the particles suspended in the oil.
Original Toyota oil filters used to be Nippondenso made in Japan.
These days there is little distinction between OEM, aftermarket, and private-brand oil filters.
Ten years ago Toyota used to have its OEM oil filters made in USA by companies such as Purolator or Champion Laboartories. Some are still made by these companies.
https://bobistheoilguy.com/forums/ubbthreads.php/topics/3570708/Toyota_90915-YZZG1_Made_in_the
Then they changed the USA-made 90915-YZZA2 into Thailand-made, Denso-branded 90915-YZZF2.
Regarding Denso I doubt they actually make oil filters these days. They probably have them made for themselves in third-party-owned oil-filter factories in Thailand, Japan, USA, etc.
I really like the Nippondenso (ND) OEM air filter (made in Japan) though. Its media is of really high quality (dual-layer) with shiny high-quality rings. Since it's a weird, odd-shaped air cleaner that sits on top of the carburetor, no aftermarket air filter fits quite right and as a result it leaves me worrying for dust leakage. Therefore, I stick with made-in-Japan Toyota/Nippondenso air filters. Aftermarket made-in-Japan Denso air filter seems identical save for the markings. Probably thanks to using Toyota/Nippondenso air filters and being careful with the tricky air-cleaner gaskets, I've never had much silicone in my UOAs. It did collapse once though, probably due to overtightening of the butterfly nut, and the lack of the metal mesh on the outside of the Nippondenso air filter didn't help.
