there is only one right answer on this subject, and i know it because of my nerd like skills, i skipped threough the owners manual one day and read that when you start getting a mildew like smell to replace the cabin filter. Now the book states that honda recommends you change it every 60,000 miles but if you need it earlier due to dusty climate or sea air wit the presence of salt then due so.
hope that helps you out.
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