Have you checked the tire pressure?
The reason I ask is because when I brought home my new Rav4, the tires which are supposed to be set at 33 were sitting at 25! Since it has been getting cooler, your tires could have lost some pressure. Definitely worth a look.
Might want to check the accuracy of the odometer in that Honda. Honda got a slap on the wrist a few years ago when their odometers in ther cars were found to be routinely reading about 7% high. Made the MPG miles look better. And a car with a 36,000 mile warranty was out of warranty after only 33,480 miles had been covered.
Even a "legal" 5% error is a lot to people that track their economy closely. A calculated 20MPG in a car with a 5% over odometer error is really returning 19MPG.