I am having a problem and I'm wondering if anyone else is having same experience? I had a 99 f-350 Ford dually 6 Speed man. with 3:73 gear had programer. It performed well and got great fuel milage. Traded it for 05 f-350 Auto with 4:10 gear both were 4X4. I was told the 05 would get 25% better milage than the 99. It get 25% worse. It has more power than 99 and drives great but my friend bought my old truck and follows me trailriding we stop for fuel I get 27 gallons and he gets 22 gallons pulling close to same loads. It has 11,000 miles now and had improved some but I am afraid to chip the 6.0 not enough head bolts. Just wondering if anyelse was having this experience?

The gear ratio in your '05 is great for pulling a trailer,but it hurts fuel mileage.I wish I had 3.73s in my '95,except for when I'm pulling a load,then I'm happy with the 4.10s.Go to www.fordtruckenthusuasts.com or www.thedieselstop.com and look for the forum for your '05 and ask about programmers and chips for your truck.I've got the name,phone number and e-mail address of a guy in Ok. that has the reputation for getting the most MPG while keeping EGTs within reason,I'll send it to you in a PM.

SaddleSore

Seems every 6.0L owner that previously had a 7.3L is singing a similar tune. For the life of me, I'll never understand why the Ford engineers went away from the 7.3.

A friend recently got an 05 450 and his story matches yours exactly. He plans to take it back to Ford and see if he can get a different software load on the PCM.

Hope you find a solution.

kp

Like flooper said, They gotta break in, When I had about 23k on my 7.3 my towing miles went from 10 mpg to 13mpg. I just put a Diablo tuner in mine ( 40hp mode ) as my warrenty is now up., my around town miliage went from 16 to 17.3mpg, on the hwy ( empty ) I went up almost a half a mile per gal, I'm now getting just over 20mpg ( 69-74mph ). But since I put the tuner in my clutch is starting to slip when I step on it hard, I guess its time to "LUK" it!

 And also as mentioned that 4:10 is gonna cost mpg too.

You can find bad apples in every bunch.  I had an 03 6.0 that they had to replace the engine in at 15,000 miles.  My dad bought 03 6.0 and has never had any major problems.  I now have an 06 model 6.0 and it is does great so far.  Once the engine was replaced in my 03, there were no more problems.  We owned five of the 7.3L Fords over the years and they were a very stout truck.  There is no comparison to the pulling power of the 6.0 however.