gas mileage
 

which is better on fuel the 4.6 or 5.4?

Too many variables to give any real data worth any value. i.e. vehicle year, 4wd, 2wd, 6sp, 5sp, city, freeway...

At best your looking at a 2mpg difference between the two engines. Check this out...it might be of help.

Real world? They are the same

to tell you the truth. it depends on your foot. if you have a heavy foot chances are your mpgs will be shat. i get an average 18.4 mpgs city according to my gryphon cs