My 2003 EX-L 4 cyd has been running great and getting 24 city & 34 - 36 hwy miles per gallon up until recently. It has 63000 miles and I've had the brake fluid, transmission fluid changed at 30000. Had the oil changed correctly and all filters changed regularly. Recently it has been running ok but at idle it runs like the a/c is coming on when the a/c is off. Mileage is down to say 18 or 19 in city and 25 hwy. I took it for service and they said the plugs looked bad. There has been nocheck engine lights of any kind but it is a little had starting where it used to start right off. The new plugs don't seem to have helped much at all. Any ideas are appreciated.

 

are you running the defroster? The defroster actually uses part of the A/C system to remove moisture and that can hurt fuel mileage a bit, you can run some seafoam through the motor to clean it and adjust the idle if you need to

 

in the northern climates the fuel companies change the additives for the fuel in the winter months.
also warm up idling can change the fuel mileage.
I always let my cars warm up until the windows are cleared off and it's nice and warm inside the car, so what if it costs a few bucks a week for the comfort and saftey.