fuel filter SHOULD be used. the problem become one of where. in the tank or in the feed line they can leak & they can get clogged. anothe fitting to be concerned with. personally ive never seen one "unclog" itself either. using them in the jug seems to work well for me & Ive very seldom had problems mostly because im a stickler about keeping all fuel lines clean. its some what immaterial if you dont follow with using an AIR CLEANER as your engine sucks in huge quanties of dust.