i am guessing it is an eclipse?

MPG depend on how u drive. under normal driving, the rating for the car is
     city 20, highway 27

     Fuel economy city  20 mpg
     Fuel economy highway 27 mpg

Raja,

An oil and transmission fluid change will not improve mileage, but will
definitely help improve the longevity of the engine and transmission.
Hopefully you also had the filters replaced at the same time.  :)

On getting better mileage, here are some ideas:

- Don't make jack rabbit starts and coast to lights, etc.
- Don't let your vehicle warm up for prolonged periods as this wastes gas.
- Use gasoline as opposed to gasohol (mix with ethanol)
- Make sure your tires are properly inflated.  Check inflation to max cold
pressure stamped on the tires
- Make sure engine is in good tune, plugs and wires are good.
- Put a bottle of a good fuel injector cleaner in the tank (I use Techron)
occasionally.
- Replace the fuel filter if you have not done so already.
- Replace the air filter (should have been done several times by now)
- Make sure your brakes are not dragging (sticking calipers will require
extra fuel)

Others can add to this list, but it gives you a place to start.  On the oil
change, in retrospect, the only way this might have improved fuel economy,
but this would be very slight, is if you went to lighter oil, say 5W-30
instead of 10W-30.  Better to use the recommended oil weight for each season
as it will offer better protection and longevity.

        Bob

Keep your foot out of it.  Yes, that is hard to do.

Are you displaying any error codes?
17mpg is awful and points to things beyond "jack rabbit" starts.
I'm getting 22 city 30 highway in a 400hp GSX running on full snow tires.

Your O2 sensor might have issues.