Re: low mpg=problem?
You can try resetting the computer so it will learn everything over again since the weather has started to change.
Clean the Mass Air sensor, run some fuel system cleaner through it, change to a lighter oil, check tire pressure. Air filter might be dirty from winter check that. Maybe the fuel filter clogged up.
No exhaust leaks?
Long shot is the car is running rich and burning through too much gas, cats are clogged up, o2 sensors failing(but with no CEL it's doubtful), bad gas.
Lots of stuff can cause bad gas mileage.