You may be having some issues with the venting/canister system. When I first took delivery of my new '01 Dragon I would notice a strong fuel odor after fill-ups until the tank was down to about 3/4 or more. Turned out one of the canister lines was pinched and damaged. After correcting the problem the smell stopped and my mileage went up a little. You may be having a related issue, like fuel in the canister from over-filling or perhaps just failure/degradation/damage.
That being said, our '99 IronMan that was purchased used with about 100K miles on it consistently gets better mileage than the purchased-new '01 Dragon.
Here's a web page with some general info on vehicle mileage, including some overview of the canister system and good methods for determining accurate mileage records: Fuel Mileage Calculation