I would join Team Mustang, but currently I only average 19-20 mpg in my short city commute. I can get 28 mpg at 70 on the highway though.
As for the Aero, the 2005-2010 mustang was ~0.37, and the GT500 version was ~0.38. The Escort has a couple advantages:
The Escort keeps the tires inside the bodywork. The Moostange curves in the body work and leaves them sticking out more.
The Escort has a more aero front end. As much as we talk about the tail, the front end hurts the Mustang. It has to build up a large pocket of air in front to try and smooth out that hood edge. My hood jumped all over the place around 80 mph, until I added more sealing on it's front edge.
The rear end of the Escort has sharp edges that give it good separation. Around the lights and trunk we have a crease, but around the edges of the bumper is a curve that creates drag.
little things, but it makes up for the same Cd numbers.
Things I want to do to my Moostange:
Lower the trunklid. The air is already attached at the trunk lid, and I think I could lower it to extend the line of the rear glass and still have it attached with low drag airflow.
remove the rear view mirrors and replace with cameras, or internal mirrors.
Adjustable upper grill block.
I currently have a lower grill block, tires at 38 psi, underdrive pulley and engine tune.