The a/c can easily rob you of 10mpg. If you were not using your a/c when you first starting driving, and are now using it a lot more, thay may explain the difference. By the way, I get better fuel economy on the highway with my windows down and the a/c off than I do with the windows closed and the a/c on, contrary to what most people claim.

Also, check your tire pressure. Tires typcially lose 1-2psi per month. If a couple of months have passed since you last checked your tire pressure, you could be low. I keep mine at 40. I have also had mine filled with nitrogen which virtually eliminates pressure loss and is supposed to help get better fuel economy.

Weight can also affect mileage. Are you driving with more people in the car, or perhaps heavy 'stuff' in your trunk?

Just a few ideas to check out...

If nothing has changed, I would have your local dealer check your car out in case there is a computer or mechanical malfunction.

Good luck!