Okay so I just filled up tonight.
Car has 610mi on it and I just went 310mi on 7.2 gallons.
My driving is nearly 100% suburban city stop and go. When I go on the "freeway" it's for 5mi tops. Mostly I just stay on the side streets though.
I'm pretty happy with that. Tires were at 36psi. And most of that tank the temps were still cold, 30s mostly.
My scan gauge guessed 6.8gal so I had to adjust it to 7.2. Hopefully it keeps getting more accurate as I go.