I'm new to this and only filtered out of the jug, until I had to pull my tank to fix a leak in a fuel line. I was amazed at how black the tank was inside. I'm guessing pressure from the muffler, I'm sure it is just exhaust residue that should not hurt anything but since then I now run an inline filter for piece of mind. I do find particles in the filter the odd time so it does work. Looks like carpet fluff, how that gets in there I do not know. lol

Mine is just before the carb.