I have a 2002 F250 7.3 the truck (117k miles) is stock with the exception of a set of larger tires and wheels and it had been tuned with a programmer for towing 6000lbs or less in "performance mode" when i bought it, so when I drove the truck home from NC I averaged 16.5mpg with a high of 17.0 on that trip. When I got home I changed the tune to the heavier setting (6000lbs +) because at the time I was pulling a 288 Sunsation. Mileage was unchanged 16.5 with or without the boat, winter comes along I decide to reset the computer to the stock tune thinking it will increase the mileage over the winter and make the truck more suitable for daily driving, the mileage drops to 14.5 immediately. I reset the computer back to the 6000lb or less performance mode and still 14.5mpg. Fast forward to this spring I rest the computer to the 6000lb. + tune since I am now towing a32' Sunsation and mileage stays at 14.5 with or without the boat, without the boat running 70 mph its turning 2000 rpm. its only 2 mpg so not a big deal I am rally just more puzzled by it than anything and was curious what others are seeing with their 7.3's

I have a 1999 f250 7.3, I put a tow tune on it. 16-17 empty 10-11 towing (formula 280ss probably 9K with trailer).

I have a 2000 F250 with Banks turbo, waste gate tune and exhaust. At 70 MPH unloaded, I get 19MPG, 75 MPH 17MPG. Try some injector stictcion lube.

When was the last time you changed the oil?

Oil change and try some lucas upper cyl lube, hot shot secret (we get it at tractor suppy) or some stanadyne fuel system cleaner. Mine likes clean fuel filters as well.

Has it been programmed for the larger wheel/tire diameter?

My 01 with only a programmer on it and 35" tires gets 15-16 normal driving. When I had the stock tires on it I got a best of 20 mpg.

Make sure you fuel filter is changed and tires are inflated correctly and aligned. Also, I believe in the winter diesel fuel gets a winter blend and it will not get as good of mileage.

Also, is this hand calculated averages?

I'll try answer all the questions at once....its currently due for an oil change I have 5000 miles on the oil and I have been running Shell Rotella oil, tires are 35" and properly inflated the computer has not been adjusted for the larger tires (don't know how to do that). The fuel filter has maybe 5000 miles on it but it seems like my 14.5 is not to far off. I will change the fuel filter again when I change the oil this time and add an injector cleaner.

How are you calculating mileage? I never seen better then 15.8 out of NAY of my 7.3 trucks ever, no matter the tune, best I ever seen with any 7.3 in general was a 2WD was 19, are you guys reading the Lie o meter overhead?