A friend of mine and I were talking and looking for filters today at our local "going out of business" Quality Farm and Fleet and both of us came to the same conclusion as it seems others have. ... the whole filter dilema comes down to a few aspects: 1) does it fit - threads are the same and gasket lines up, 2) is at least as large as the one it replaces and have oil passeges at least as large and as many, 3) does it have the same anti-backflow valve/diaphram. ...That's it!!!
Maybe we've oversimplified this but I long ago went to the Ford/Motocraft FL-300 and the Puralator or AC equivalent which is slightly larger than the $8 Ford/NH dealer filter and which still aligns perfectly on my old 1720. I'm only guessing but since this filter was used on much larger 6 and V-8 engines, I've assumed it is at least as good. More recently, my TC-40D came with a filter that was the same size as the one on my 2 cylinder Kohler engine-driven gas lawn tractor. No way that filter was as good as any of the larger alternatives. I think I'll stick with the FL-300 and equivalents. Any thoughs?