Not familiar with the 5.3 Fuel Milage I am sure it gets a few miles to the gallon better. I drive 10 Miles one way to work with 7 stoplights, i really dont consider it City driving. I check my milage all the time (as it makes me drive better) I average 15Mpg all the time. Hwy (doing the speedlimit) i get 17or18. This is considering i drive in the Ozark Mountains everyday so i would imagine if i lived in the flats of Kansas it would do a little better. Caution!!!! i drive this thing like a granny merely to get good fuel milage. However its nice having the power!!!!!!!