Quote:
Originally Posted by jphughan
Nice write-up OP! But if one of the four filters does nothing, does it need to be replaced? I assume if it's sealed off from any air flow, it should never get dirty, so I wonder why BMW doesn't just sell them in sets of 3 and have a dummy bit of plastic in the fourth slot....
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hmmm i just replaced mine and all four are dirty same amount of dirt. I would replace everything... i think its there for a reason. if not then i have no clue why all four of my filter are dirty... im sure it works.