There are two I4 Accords in the database. Why not check them out ?
I'll warn you that Xcel's results with his brand new I4 sedan are a bit atypical - he's one of the very best at squeezing every drop out of a gallon, no matter what vehicle he's driving. I daresay he could get 25mpg with a Hummer H2 (just over 2x it's 'real-world' rating, as it's not subject to EPA testing)
That being said, I'll guess about 30-32 in mixed driving with the I4, and 24-25 with the V6. I had a '01 V6 coupe, and got 23-24 pretty consistently in 'normal' (not hypermile style) driving. The 7th-gen Accords are slightly better rated, mpg-wise, than the 6th-gen. People that report on their mileage on the Accord forums post higher for all-highway trips... from 39-42 with the I4, and about 30-34 with the V6. This is, of course, depending on several factors; chief among them, speed.
Comparing the current I4 to the HAH, EPA-wise, the HAH comes out on the plus side by 1-2 mpg on both city and highway. Meaning that you have the potential to (& eventually should) do *better* than the I4 car, once your engine is broken in. On your 3rd tank, it's not, yet (look for initial break-in between 1200-1700mi; you'll know when it occurs).
Finally, I'll guess that had you gone w/ the I4, you'd get significantly less than the EPA rating with that one as well, at this point in time. Sorry to be judgmental, but at this point, I'm thinking the car is fine...it's the driver or the drive conditions that's at fault
