That's great mileage!!!  I've been checking mine by hand too and after a bunch of tank fulls where I hit right at 25.5 MPG;   my last tank got 26.4.  I'm at 2,800 miles.  I was hoping for 25 when I bought it so I'm pleased.   

i recently drove from Louisville, KY to Wilmington, OH.  i had a full tank when i started, and i made it all the way up there and didn't touch half a tank...
http://maps.google.com/maps?f=d&saddr=Louisville%2C+KY&daddr=Wilmington%2C+OH&dirflg=r&utm_campaign=en&utm_medium=ha&utm_source=en-ha-na-us-gns-trs&submit.x=143&submit.y=15
this was a 2.5 hour drive...and i did 80mph the whole way...sorry state troopers!!!

Running 19" staggered wheels.. 235 front and 265 rear, its got about 4300 miles on it now, had it since Feb. Average city is about 23.8 and average hwy is about 25.5. Modified with cai, headers, s-pipe, and exhaust.

A/T, all city, 20mpg

Car:
In possession for 3 weeks.  2,000 miles (as of TODAY!):
60 mph-> a bit over 31 mpg
70 mhp-> a bit over 29 mpg
80 mph-> around 26 mpg

So, it looks like optimum mpg is somewhere around 60 mph.

I am not a "gentle" driver with the gas pedal and I live in the "foothills," so there are constant up and down hills.  Those up and downs hurt overall mileage.

So far actual average mpg: around 26.
That is highway, high-speed interstate, mountains, downtown Atlanta and around the town where I live.

In a few thousand miles (5,000-10,000 overall), if all goes as I have been told, I fully expect it to get better.

I have checked the mileage on 3 tanks. The first was 31.4, second was 29.5 and third was 28.8. All figured with calculator.

I'm seeing the on-board computer report about 1-1.5mpg higher than reality as well.

I have about a 50-50 city/.hwy mix and I'm getting about 25-27 avg.  I recently completed a Mobile, Al to Detroit, MI run (just over 1000 miles each way) and I got about 28-29, averaging around 70mph most of the way with a few traffic slowdowns in the cities I passed through.  I ran the A/C most of the way.

This car does really well on the highway, but I agree with what other's have reported already - any idling, especially with A/C on really drags the average down quickly.  Also - I live in an area that's pretty hilly - I lose a LOT climbing those hills and with the sort of torque-braking that this car does going downhill (auto trans) you don't really get the opportunity to gain mpg on the downslopes.  I find myself sometimes slipping the car into Neutral going downhill just to eliminate the engine braking.

--Chris

These were all manually calculated.