Increasing F-350 efficiency
 

I'm driving my Dad's 2002 F350, (quad cab, duallie, 4wd, automatic). Till my Mom gets out of her wheelchair he's traded me for my minivan.
The truck gets 9mpg according to the onboard computer, 11ish on the highway. With fuel economy that low even a small 2-3% increase would pay off pretty fast.

Do the typical air intake, exhaust, programmer mods actually improve fuel economy if you keep your foot out of it? Wondering what works and what doesn't?

While I realize this is hardly the typical ecomodder vehicle, I'm hoping someone here has been down this road. Over on the diesel truck forums guys are primarily interested in maximum power, regardless of fuel economy.

Is it gas or diesel? If it's diesel, it should be getting significantly better mpg than that.

Regardless, improvements in driving technique are going to yield the biggest gains short of significant modifications, and are the easiest things to do.

Check the tires for uneven wear as a first step in seeing if it has proper alignment as it's common with work trucks to torque the frame while towing or using a snow plow.
It's also most likely about time for a fluid change, synthetics all around, check into getting a shop manual for it and read their list of mantainace suggestions.
Thing is, your truck is in the class of commercial duty or heavy duty trucks and does not have any EPA numbers because of that, there for it's not regulated and the mileage you are getting is most likely close to what it was designed to get.

Lazy truckbed aeromod.
 

Maybe you could try something like this. The idea is to allow smoother flow in the trapped vortex, and still be discrete and simple and practical and all that.

The blue lines in the image are just bent plastic rectangles.

Or he could try what's been proven- a 1/2 tonneau or a full one.

Or better yet park the dang thing and get something realistic to drive.

If it's a diesel a hotter thermostat should help.

A larger less restrictive exhaust won't help MPG.

True, but that's not nearly as interesting :)

(Do full tonneaus even work for mileage? I remember reading that they don't)

Sounds like you need to study up on it then.

with the aerodynamics of a barn and how heavy that thing is driver modification will yield some pretty big improvements.

Slowing down such that you don't have to use the brakes much except to stop where required will be huge.

Reducing your aerodynamic loads by reducing velocity will help a lot as well. can you go 55 in stead of 65?

depending on how long your going to be driving the f350 a cheep econ-o-box in the 500 dollar range may save some cash then sell the thing after you get your van back. please don't misunderstand as I realize a full size and very capable truck has it's place.

The performance mods, while they claim to increase mileage really don't do much, it requires a certain amount of energy to accelerate a mass and overcome the drag. performance mods can't change or reduce those energy requirements. They really only help at high power settings and that is not where economy is going to be made.

Make a tonneau cover, a partial grille block, and a front air dam that shields your undercarriage. Raise your tire pressure to 5 psig above what Ford recommends, or to the rated pressure listed on the sidewall of your tires (whichever is lower).