The dealership told me I need to replace it and wanted to charge me almost $40. I figured I could do it cheaper. Is it easy to do? Best place to buy a replacement?
Very easy! You can pick one up thru amazon or local auto part store for about $10. At least for the Gen III and the prius v (wagon) the filter is located behind the lower glovebox. The glovebox pops right out (directions are in your manual). The filter is located behind an easily removed cover. Just slide the old filter out and the new one in. It's a five minute job. Definitely a do-it-yourself job!
Or, if it's not too far gone: slide the old filter out, knock the dust off it, hit it with some compressed air, and re-install.
it's a pia to remove the glovebox door and replace it. terrible design, but i diy it. take the old one out before replacing and check it as mendel says. be careful of aftermarket filters, there are good ones and bad ones. i stick with toyota, cause i like the charcoal filter for diesel exhaust and what have you. that's what comes oem. 'the pleats are a little bit bigger, but it should do the same job'. no. why use pleats at all? note the airflow direction when you take the old one out, and reinstall correctly. use caution with the filter cover latch, some have broken them off.
Go on to You Tube and bring up a video on how to change it. It will give you detailed instructions as to how to do it.
Be very careful when you do it. It is very easy to break the clips on the housing that holds the filter.....
I replaced mine only because I found evidence of chipmunks in the glove box and it was very dirty. Normally I just knock the dirt out of air filters of any sort, and reinstall them. That will save you $10 more.
The function of the pleats is to increase the surface area. The surface is what tends to clog up first. By having more surface/unit of air you get a longer time before failure.
I used to replace mine yearly on my Gen 2 but I don't take my new Prius into that dirty environment as often as I used to. A steel mill is a dirty place to take a car.