There is a similar thread in the General discussion area that goes more through all this stuff....

 

Try this... Get a new air filter. Then disconnect your battery (-) negative cable for 5 minutes. Reconnect it with the key OFF and out of the ignition. Start the car and let it idle for a few minutes, then go out and drive the hell out of it a little bit. (WOT a few gears, touch the rev limiter once or twice.) Then a few minutes of easy driving. This should unlearn any bad habits the PCM picked up by erasing and resetting the adaptives and APPS values. Also, ask the dealer if there are any TSB's or flashes applicable to YOUR car, and ask him to do an APPS (Acellerator Pedal Position Sensor) relearn. That can only be done with a Mazda scan tool. This shows the PCM (computer) the full range of the gas pedal.

 

My 3 had bad gas milage in the first 3 months, I felt like I was driving V8. LOL
After that it feels like Geo Metro, I drive it for two weeks in the city on one tank. I think it is only in the begining that you get bad gas milage.

 

i just bought my car a couple of weeks ago and i get 30-34 mpg driving to work half city half highway everyday. one night i went cruising in town and alot of high rpm and only got 18 mpg. i think thats what your problems are probably. i know its fun to race around but not good for mpg.

 

I have a 5-door with auto. It started kind of crappy also, ~20-22MPG overall. After about 1200 miles, things settled out, 21-25 if the tank is primarily around town. 26-29 with only highway, 70-80mph. This is with the AC running constantly. This is about what the sticker indicated, 22mpg city, 28mpg highway. The 5 speed get a couple better.

Something else that can affect mileage is tire pressure. Keeping the tires properly inflated can make a difference of 2-4mpg or more.