I can not comment on the Edge MPG as I just bought one (only 58 miles on it so far and still breaking it in). I do know for those that have auto climate (I have dual zone), that when I place it on 60F, it kicks the AC on - even though it is 25F outside...odd, but that will kill MPG. 65F does not kick it on, but is still warm to me. Another thing is I noticed is there is no engine splash guard. While they are annoying as sin to work with when doing Oil changes, it does help the air flow under the car - I am curious if anyone could fabricate one.
I do want to say, the Brand of gasoline DOES matter. I did tests in my Mazda 3SP during summer months. I used BP, Shell, Speedway, Clark, Citgo. My testst were 10 fill ups of the same station same pump and driven as similar as possible (first two fill ups not counted and used the last 8 fillups in calculations). Average miles per tank (14.5G total capacity) was 363 Miles with an average fill up of 12.8 US Gallons. I used regular octane and started at 2604 Miles on the engine. I suffered as much as I could during this test but I did use AC at times, but noted that. (I am anal if you did not figure that out).
Note: I did lots of mixed driving. My Mazda now has 68542 miles on it (bought in May 2005). I do not drive like a bat out of hades, but will Zoom Zoom when I need to. I have a 5 speed manual.
The best gas mileage by far was Shell (my location is Ohio). It averaged 1.8 MPG MORE than BP (second best).
Shell: 29.765 MPG
BP: 28.048
Speedway: 27.495
Citgo 25.457
Clark 25.023
I tried my best to keep variables constant - but keep in mind this is not 100% accurate. Variables such as type of station (heavy or little usage), temperature, driving style, regional location (yes gas formulas are different for regions), winter gas, and others affect MPG.
Basically the moral of the story is buy good name brand fuels.
Again, this is my $.01 so take with agrain of salts
Solas