Hey, I'm posting up to get an idea what you are getting for mpg's on your truck. Iv only had experience with the 3.8 and 4.6 mustang motors and never had the 5.4L triton motor. So I don't know what's normal. I'm getting 13-14mpg on almost all highways (65-75mph). Does that's seem normal? Because it doesn't to me. No mods to the truck. Only change is the tire, I'm running 285 nitto terra grapplers.

 

It might be a little low, what are the specs on the truck?(cab config, gear ratio, 4x?, year, miles). Was the PCM ever reflashed for the change in tire size? It could be giving you an off reading on miles. Keep up on proper maintenance and go from there.

 

I have 35" mud tires on mine and was getting about 8mpg then I added exhaust, intake and edge programmer and im at 12 now... thats mostly stop and go traffic

 

Yea sorry, it was an early morning

4x4
5.4L
Stock 17" rims. 285 nitto terra grappler tires
No exhaust, doesn't feel like it has a tune (I have an sct tuner on my mustang)
Ext cab. (2 doors and 2 half doors)

 

that sounds about right to me. ive got a 97 5.4 and with 31s and i get 15

 

Yeah i have a 99 with 265 65 17s and i get 16 on the highway tops
Same set up as you ext cab 4x4, it does have 209k on it though

 

Since the government has forced ethenol on us my mileage has dropped from 16 MPG Highway to 13.4. Stock rims and size tires, K&N air filter, tornado air flow enhancer, and cat back dual exhaust. Thanks for nothing government.

2003 5.4L F105 Super Crew Lariat 4x4

 

Dayum, my 4.6 trucks knocking on 18-19mpg's on the highway in the summer. I used 1/4 tank to go from Lima OH to Cleveland, OH, which is about 3 hrs. Glad I stuck with the 4.6 now lol...

 

ill take my 12 mpg 5.4 over your 18 4.6 anyday

 

Wow. Well good to know. And I have 95k btw.