03 F-350 Dually, Diesel question

[zippsuperman]

Since day one, (last October) bought with 528 miles. our overhead computer has never read more than 14.8 mpg. That was the first 2 weeks we had it. We have been told time and time again you will see it jump when you get above 15k or more. Well we are now at 24k, it has not been in the 14 mpg in 6+ months. Everytime we get diesel and there is another Ford 350 fueling up I ask what their computer is showing. You guessed it, virtually everytime I have looked in the cab it is 15, 16, 17 and as high as 18.3mpg. Recently a gentleman told me the only time he is down where I am is when he is towing his travel trailer. Took it into Ford, they said dyno is reading 17-18 mpg. They said they will have to reset the overhead. Got it back, filled up, 698 miles to empty which is on target, switched over to mpg, 13.3. Does anyone know what is wrong because the techs at the dealership don't? Further, when we fill up, I make sure it is topped off when doing so that thing is between 450 to empty, up to what is was last week after leaving the dealer 698, and that is the highest reading ever.

Also slight vibration side to side randomly while on highway. Ford says nothing is wrong, it did not ever do that in the first 20k, that steering wheel did not move.

 

[Whit]

Does your overhead read the same mpg as hand calculated?

 

[zippsuperman]

03 F-350 Diesel Dually

I do not figure it out all the time manually but when I do it is not even close. I am not complaining about the mileage as I think it is where it should be, but we are thinking about getting the 05 or waiting to 06. If someone gets in to drive it and sees 16 versus 13 it will make a big phsychological difference on their decision making process.
It just drives us crazy when we peak into others cabs with similiar year, and mileage and our is always 3-5mpg lower on the computer.

Thanks

 

[Whit]

So hand calculated does come out higher?

 

[Swany]

If you're running any tuners, it will throw off your overheard computer. If you aren't, that's pretty damn good mileage for a dually!

 

[Dieselmaster]

Like all the others have said... What does it work out to by hand?

Dually's usually have the 4.10's so they usually will get a little lower on fuel mileage.... A lot of guys will reset the overhead everytime they refuel...this will give you the most accurate reading per tank... otherwise it becomes one great big average....

I also didn't notice if you were mainly in town or highway miles.... I would expect your intown to be right around 13-14... highway miles running empty around 15-17....

If someone gets in to drive it and sees 16 versus 13 it will make a big phsychological difference on their decision making process.
It just drives us crazy when we peak into others cabs with similiar year, and mileage and our is always 3-5mpg lower on the computer.

If it bugs you so much just do like I do since mine doesn't work right because I run a chip.... just set it to the temp....

Or if your looking to sell it then reset it and find a great big hill and coast down it.... this always throws it off and will show you getting 30-40 mpg...