It´s always good to be helpfull, and I forgot to metion that there is another really important thing the air filter in your air compressor. You sould clean it regularly and change it when it's really dirt or at least once a year, especially if you have one of that filters made of foam. If clean and change you car's air filter why shouldn't you do the same to your air compressor?
My advice is to buy 2 or 3 filters for your air compressor to keep as spares, that way you won't be so lazy to go out to buy one when you see that it needs replacement.
António Costa from Portugal
P.S: sorry for my bad english