6.0 MPG, Help me before I trash it

Just avoid the grief of keeping that engine. Put a 7.3 or Cummins in that truck or buy a LBZ or 5.9 Cummins the conversions are done now as those components are on the market and becoming more common. Just have to make the goal of dumping the 6.0 the future expenses to make it reliable are too high. Ford had the ticket with the 7.3 and now new tranny options are so reliable that your truck could be modified to run for a long time. People spend so much trying the next new one and chance the old wish I didn't spend $55k on this 6.4 and only getting 12 mpg max!!! That's a pizzer now to me... I have the LBZ and it's just what this house needed. Every driver needs different options for the lifestyle and work they have so I just mention mine for the example of satisfaction and great mpg and reliablility so far. New GMC LMM owners are deleteing the DPF with straight pipes/mufflers systems and getting 21 mpg with Quadzilla programmer that fixes the alarms/signals from computer. Cost is less than $1k and they keep the front pipe to install for the emissions test day. They just make the pipes match with the same flanges so it just unbolts and they plug in the wires for that purpose. No Ford can convert like that for that low price I know of if you look at the 6.4 to LMM trucks. good luck...  

check ur tire pressure  

Well my 99 F-250 space-cab auto 7.3 gets 15.2 to 15.7 mpg and I'm always driving 65-75 when I'm not stuck in traffic.  
2008 F250 SUPER-CAB 6.4 PSD 2WD 1999 F250 super-cab 7.3 PSD 2WD(sold)
MEMBER- BLOWIN' SMOKE GANG Commerative Heart

Intake and exhaust would definetely help! The tires you have make a big difference! You need to get 265s or 285s.
And don't rely on what your computer tells you what kind of mileage your getting its not accurate! I've payed attention to each of the three trucks computer system and fords is very inaccurate people with dodge and chevy's will always say they get better mileage because their computers only average it out while they're actually driving ford's computers takes in the average of when its idling in with the average of when its driving thats why it also shows less! Dodge and chevy also average it out over a longer time than ford does! But the 6.0 does use more fuel that the 7.3 I've tried it!  
Member-Blowin Smoke Gang

There is a fuel addative made by Power Service called Diesel Kleen that will raise your Cetane by six numbers and that is what you want in a fuel addative Cetane is kind of like octane.  I had a 99 f250 and when climbing a hill near my house with the cruise control set and the addative in my tank my truck didn't need to down shift to hold the speed limit.  When you add power that way you then you MPG's along with it.

With diesel's you want the least restriction possible on the intake and exhaust.  No backpressure required unlike gas engine exhaust's. K&N and AFE both make cold air intakes that will help. If you have O2 censors on you exhaust then your options are a little more limited.  But if not then you can always put a delete pipe in place of your cat and you muffler to free up some flow. My 99 was strait piped and it sounded like a big block with duals and flow masters.  

I now have a 06' dodge diesel w/ six speed stick I have a K&N cold air intake and I removed my muffler but left my cat, I also run the fuel addative I told you about.  I get 18 around town and 22 on the High way NO LOAD as long as I keep it at 65MPH.  Towing approx. 7500 lbs I get about 19-20mpg Highway.

By the way when you pull across country pay attention to where you fill up. Some states Like Oregon require pump fuel two have a biodiesel blend.  It won't hurt anything but your MPG's and power but that fuel addative will really help when you run into this. Synthetic Diesel engine oils can help a little also and not to mention extend your service intervals.