I have a 5.4L SuperCrew 2x4 and am only getting a little better than you. I do mostly city driving and get about 15mpg. On the Highway about18-19mpg but thats using the cruise control. There was another post about the 4.6L tips for better gas mileage you should look up becuase I think the tips would apply to the 5.4 as well. Here is the link to that thread.

https://www.f150online.com/forums/sh...hreadid=107999

 

I've read that if you turn off your OD when driving in the city that you can get 25-30 extra miles to a tank. Just run the Over Drive when on the freeway. My next fillup I'm going to try the technique and see what the results are.

 

Interesting point. That OD kicks in way to fast, expecialy when it's cold. I think I'll try that myself.