No changes in driving habits or city/highway ratio, air is on a majority of the time but that isn't anything new. (I live in FL it's always hot!) Car has 63k miles, K&N filter, tire pressure is 32. Will try fuel system cleaner. Thanks for the advice!

I've had my 2005 Vibe base automatic for over a year now. The first year I consistely got 32-33 mpg with 87 gas. Now I consider it a good day if I get 27. No codes, no lights on dash. Regular oil changes with synthetic only. Any ideas on what could be wrong?