You can all check & rule out some of the normal things that cause poor MPG.

- dragging brakes
- tire pressure
- suspension alignment
- I'd say tune-up, but we're talking about a NEW car...
- do you let the car idle to warm up? (during idling it gets ZERO mpg)

Using the heater shouldn't do anything because that just uses waste-heat from the cooling system.

 

is your accord a v6 or I4?

mpg = miles drove/gas used(actual from pump)

i just picked up a 2011 EXL I4 on monday (first honda!)... I have about 270 miles on my first tank of gas and havent touched the halfway mark on my guage

 

I have the I4. Had my first oil change about a month ago. As the weather got warmer the mpg rose. I get about 27.5 mpg. Again, this is with slow acceleration. I'm at about 8600 miles. Even with extended trips I get 29 mpg max. I reach half full at about 230 miles.

 

See, your mileage is improving as the vehicle ages. Honda's really do take till about 10k to break in. My I-4 EX-L navi bought 12/16/2010 is now at about 13500 miles. On my commute which is 95% highway driving I typically get 33 to 34mpg per tank (according to the computer built into the navigation unit and spot checked doing the math in my head). I reset "Trip A" on every fill-up. "Trip-B" I have left as-is the entire time I've owned the vehicle and it is currently showing a lifetime MPG of 30.1.

So overall I am getting the mileage I expect to get based on the window sticker and my type of driving. If you really think there is something wrong with your car, take it in to be looked at. But I suspect it's a combination of not being entirely broken in and your driving not supporting the high-end of the estimates. You shouldn't be getting as good MPG as I do just based on what little you've posted. For example, your driving is either more "city like" than mine, or you take many more "short trips" than I (short trip as defined by a trip that barely even got the engine up to operating temperature). You are at 8600 miles now and say you had your first oil change a month ago. That would have been at what, 8000 miles? To achieve the MPG I'm seeing I really am driving the strictest defination of 95% highway. My maintenance minder didn't trip to oil change required until 11,500 miles.