I used to be religious about changing the foam rubber filter element in my Universal M12, first yearly then every 2-3 years and I would see it did not have much wear and I did not use the engine so much so I figured "what the heck, why bother" until I was reminded by some owner who brought the subject up on this forum. Good thing I took a look as mine was 1/3 disintegrated, gummed up on the steel mesh frame and of course some had to have gone into the engine. Gotta love Diesels, they take a lot of crap. Anyway, I say this as a reminder to those who might be as cavalier as I was that you need to pull it apart every once in a while and replace it or more appropriately in line with how many hours you put on the engine, maybe more often.