i bought my 2.3 s model new in 2006 and now have over 170k on it,the car has been a pleasure to own with absolutely no major braek downs except 2 trailing arm bushing in the rear suspention that costed me roughly $400.00 to repair both.ive used nothing but conventional motor oil with regular 3k changes and the car runs as smooth as new and doesnt touch a drop of oil.but like alot of people on here,i wasnt to thrilled with the a/c. although i dnt think mine is as bad as some people say theres is,i still think it could be better.anyways over time it seemed to get worse and worse,even tho the air comming out is very cold the car didnt seem to wanna cool.after calling several mazda dealers and them all saying it would cost me a basic $96.00 to have it looked at with no other possible causes,i called one last dealer that a friend recommened to me.young volkswagen-mazda-dodge in easton pa the service guy asked me if i ever had the in cabin air filter changed,now i know i may sound like an idiot, but i didnt even realize it had one.well let me tell all you guys that have any issues with ur a/c.if you havent had yours changed,do it.my filter was totally blocked,full of everything you can imagine, this made a signifigant improvement with my a/c not to mention the airflow comming out of the vents easily doubled or tripled,no lie. the dealer didnt charge me a diagnostic fee and only charged me $20.00 to install it and showed me exactly how to do it.i never owned a car befor with an in cabin filter and iam still shocked what a difference this made.

 

Hah!
Just reading your headline I thought that's an easy one!
Thanks for sharing!

 

Without reading the post my first thought was pollen filter.

they should be changed every two years or 40,000kms.