K & P Engineering filters
Confirming what others have said, I had two of the Challenger filters on my Baron many years ago. The Baron is gone, but the filters live on, one is on my wife's Explorer and the other will go on my RV-10 IO-540. They're very high quality filters. I liked them so much the I have them on my BMW motorcycle and my F350 diesel as well.
The Challenger filters are made by K&P and sold as the FAA-PMA version, but you can buy the filters, and parts, on USAoilfilters.com, except for the housing. For an IO-540 (or probably pretty much any engine with a 3/4-16 thread) you need the following parts:
Housing: C4 - this has a 1" nut on the top and safety wire holes...they are appropriately cautious about not violating their PMA agreement with Challenger, however, having held both the PMA housing and this one in my hands, it appears to be only lacking the Challenger name and FAA-PMA laser etching. You need to call K & P Engineering directly to buy this part.
C4 Housing
Filter element: FE-15 - 3/4-16 thread. If you happen to be using a metric engine, such as a UL Power or Rotax, an FE-30 element will fit the housing with a 20x1.5 thread.
Spring: FE-RS1
Quad Ring: QR2 (they're about $1 each and can be used multiple times, just inspect for wear before reusing - flip them over for additional use)
If you're spending $30 on a filter that you're tossing in the garbage every four months, the break-even cost on this permanent filter is about 7 oil changes. But the price, to me, isn't the real value. The permanent filter has a 35 micron rating, which stays constant throughout the filtration period, unlike paper elements that open up during the same period (for a good time, read the certification spec for paper oil filter elements and discover the wide tolerances allowed).
Also this filter flows much better than a paper element with a 'little' extra cooling coming with the fins on the housing; at the very least, they
look cool
The main benefit to me isn't the cost, or the reusable factor (both very nice features though), but rather the ability to quickly pull the filter apart and inspect. The element has a rare earth magnet, so it is immediately apparent if you have ferrous material, and inspecting the rest of the element is very easy and quick.
I then clean it with some mineral spirits (although parts cleaner in a can is recommended as well), wash with simple green, rinse with water, air blow it dry and reinstall. I read in a former post about some limitation of 5 years from ACS - I have to assume that is some legal limitation, but there is no limitation from K&P; the sucker is made from billet aluminum with stainless medical mesh in the filter element - not sure what would why it would need replacing, other than damage, with the only wear part being the quad-ring that is reusable and inexpensive as well.
Highly recommended.