I own a 2005 Chevy Cobalt and I've had it since it was brand new. It has the 2.2 liter engine and about 23,000 miles on it. I have been noticing that my fuel economy has beengradually going down in the past few months. According to the digital fuel economy gauge it's gone from over 29 mpg to a little over 25 mpg and it is still going down. Are these gauges accurate? I try to keep my tires at the proper air pressure, change my oil every 3k, do all my maintenance,etc. I noticed it started going down after I had some work done to it(bad wheel bearing and brake pulsation). With the low mileage on it I doubt it needs a tune up. I was wondering ifa clogged air filter or fuel filter may be causing this problem although I checked my air filter and it looks fine. Any input on this problem?

With 23,000 miles on it, a tune up couldn't hurt. When was the last time you had an oil change?