2001 4x4 2500 6L

I'm still getting 9.6 miles to the gallon around the clock. I was stold that I should be getting between 11-15.
1.Replaced plugs and wires with factory parts.
2.Put in a new air filter 3.Changed oil to 5W-30 Synthetic
Will a tune-up at a shop still help even though I already replaced the plugs and wires?
Will changing the Oxygen sensors actually help? (Expensive) I also tried before on a 1994 Z-71 and saw no difference.
I unplugged the MAP sensor with the truck running and the truck ran real bad and when I plugged it back in, the truck ran fine. Could I still need a new one?
What should my next step be? I really like the truck.
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My brother in law was having terrible mileage issues with a Ford V10. The best he could get was 7 mpg. He did the same as you, changing out various parts. Finally he brought it to the dealer...the computer was faulty. His mileage doubled.
I think you can throw parts at your 6.0 until the cows come home...You need a "good" mechanics help.
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Do you still have the stock size tires on (245/75/16)? If you changed to larger tires without reprogramming the PCM you are traveling more miles than the odometer indicates. You may just have a MPG calculation problem.

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On Sat, 08 Apr 2006 19:41:26 GMT, "calhoun"

THis is close but no cigar. If you have lifted it and have oversized tires, not only is speddo calibration off but the bigger tires and/or lift require more power and fuel to overcome and it is usually the reason for poor MPG problems. Driving habit and overall gear ratio for load and engine type play a roll too here. ----------------- The SnoMan www.thesnoman.com
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I did by new Firestone 285/75r16 tires. The front torsion bars were raised when I bought it and I have since lowered them down and put new shocks. I was hoping that this was not the cause of the 9 miles per gallon, I could understand 13 or even 12. I had a 1994 Z-71 and was getting 13 around the clock with 305's. I also believe that the 2500 does have a different differential ratio than my Z-71. But should I be getting 9-10 in the city?

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The 6.0 is not very fuel efficent in town and if you are running 285 with 3.73 gears. town MPG will suffer. If you have chopped up the exhaust for duals that can murder in town MPG too. Below is a link for a tire size and axle ratio calculator
http://www.snoman.com/HTML/axlecalc_5a.html ----------------- The SnoMan www.thesnoman.com
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As stated before, if you didn't reprogram your PCM you are traveling more miles than your odometer tells you. You are traveling about 113% farther than indicated. If you calculated 10mpg you are really getting 11.3mpg. You can't compare the mileage of a Z71 to a 2500HD. The HD is over 1500 lbs heavier and has a taller rearend gear.
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