4.6L Gas Mileage

16.5-19 city depending on the temp, my tune and how much I use the A/C.
I got 27mpg on the highway with my stock 3.27's, best I have seen now is about 25ish with the 3.73's.

My mpgs went up with the trickflow TB and Plenum BTW. I usually don't let my tank get past 1/4 full, just because I have a problem with that. I haven't seen what the low fuel light looks like! (I am slightly anal...)
 
My 2002 Gt gets around 20-21 mpg on regular 87 octane with mixed driving, and 22mpg on 93 octane, mixed driving also. Its also a 5 speed car.
Highway around 25-26 I would think, have not took a pure highway drive to burn a entire tank of gas in it yet.

Its actually great on gas I think, better then any other car I have had.
 
I have not calculated mine since I got the car. I normally dont let it run down below 1/4 tank, but always seems when I put gas in it has like between 1/4 and 1/2 tank, but usually Iget like 150 miles to half tank at least, and yes, I do get on it :D Not bad for a crappy old tune....cant wait to see what it does with the new tune. The previous owner said he got 24 mpg on a highway trip:nice:
 
well I Googled this and apparently "mileage" means how many miles can on go on a gallon of gas...? as a Mustang owner this is a new and foreign concept to me.

Seriously though my car gets about 8mpg in the city when I drive it.