I had A 96 F350 PSD that got 14 mile around town no matter how I drove it or towed with it.
I now have A 02 F350 that never got better then 12 on the highway and got aroung 8 miles when towing. I installed the Diablo predator and got 14 miles in town. I went on A 3.5 hr trip from NJ to Lake George and got 16.5 miles. It is geting better but would still like more.

 

Many of the PSDs (I believe only Superdutys have this problem)are unfortunately getting air mixed in w/ the fuel system. Diesel injectors prefer a solid gulp of fuel as opposed to fuel filled w/ air bubbles. This causes a rough running truck that often gets poor fuel economy. This, many believe, is the primary reason that 2 identical PSDs often get vastly different mpg and often sound considerably different. This problem can be corrected thru a series of relatively simple mods to your fuel lines and your mixing chamber inside your fuel tank. You should research the subject @ www.texastowncar.com . You will have to register to get access but it is free and they will not try to sell you anything. I bought a simple kit for $35 that came w/ all of the instructions to do the mod. Several people sell the kits. I bought mine from JNB. (sorry, but I don't remeber the web site) There are instructions on which parts to buy but then you have to figure out what you are doing and that could take a lot of time. Better to buy a kit. This helped smooth my truck out considerably and improved my fuel economy as well.
The TAG is a simple device that is inserted into the intake to smooth out air flow and seemed to do wonders for my truck. At least, it worked very well w/ my mods. i wouldn't drive my truck without it.
The stock thermostat is 195. Diesel fuel likes to be closer to 205 to fully combust. That is why the International version of the PSD and just about all big rigs have thermostats in the 203 degree range. Have you ever noticed how your truck smoothes out as it warms up? Well it will smooth out a bit more w/ the thermostat. By the way, older PSD (pre-99) come stock w/ 203 degree thermostats.
Good luck guys.

 

I have been fortunate, as my truck has given good mileage since new. I have a 2001 F-350 dually, 4x4 crew cab with the 6 speed and 3.73 gears. At about 5000 miles I had some mocifications performed which have only helped the already good fuel mileage.

1st: My first change to any Diesel has always been the addition of extra gauges, specifically Exhaust Gas Temperature -EGT, and turbo boost pressure, as well as transmission oil temperature for an automatic. These gauges allow you to see what sort of a difference any later changes make, as well as help you to see what your driving style is doing to your fuel mileage. If you can keep your EGT under 600 degrees and your boost pressure as low as possible, then you are doing everything right.

2nd: Air flow. A less restrictive air filter and larger diameter exhaust with a straight through muffler make your engine do less work to draw the air in and to push it out. If your engine is doing less wasted work, then that work is now available to move you and your load faster or further with less fuel. somdbody once likened our Power Strokes to a marathon runner inhaling and exhaling through a soda straw.

3rd: Chip. A quality chip can improve fueling under just about all conditions. They will make a new truck out of that clunker in your yard and improve fuel mileage at the same time. Unless you plan on seriously overloading your truck with a 16,000 pound trailer or some such, I wouldn't recommend more than a 60 to 80 hp increase.

4th: Parasitic losses: One of the biggest of these is your fan. The factory viscous clutch still has the fan turning hard most of the time. An electric fan clutch will free up somewhere in the order of 25 to 35 horsepower. This is power that your engine is already making. At most any forward speed, you are getting enough air through your radiator, even without a fan. By taking the fan out of the equation, you are now saving all that fuel that it took to develop the power to run the fan. Most good clutches come with sensors to turn the fan back on if it is required by either the transmission, the engine temperature, or the air conditioning. And a great extra is that you can turn the fan back on during a steep heavily loaded descent and it will slow you down, because it now demands that extra horsepower from your engine which is not receiving enough fuel to produce it.

With all of these changes, my fuel mileage is now
58 mph sustained highway travel - 20.5 mpg
70 mph sustained highway travel - 18 mpg
Around town stop and go - 16 mpg
4200 pound slide in camper at 35-50 mph on back roads - 14 mpg
NO complaints here.

 

Sunhester, what is a TAG and where would one find it? maybe you can explain what the fuel tank mod id and what its suppose to do. the texastowncar site wouldnt open up for me.

 

I got a 2001 PSD F-250 4door shortbed, only mod is a banks trans-command, at 70mph getting 19.2mpg, towing #8000 fifthwheel,getting 11.2 to 12.6. Unloaded I've gotten as high as 20.2 at 60mph. Thats my story and I'm sticking to it.
John in Tampa

 

oops, forgot the other mod, pyro-boost and tranny guages.
John in Tampa

 

Many PSD's have a series of leaky seals and such that allow air to become entrained in the fuel. This is bad. Some PSDs have picked up 4-5 mpg w/ this upgrade. Only the worst ones will see this kind of improvement. Some of the mods are under the truck (prepump mods) and some are in the fuel tank (in-tank mods). To learn more about JNB tank kits do a search on the web. They are out of AZ I believe. I paid about $35 for a kit that came w/ great instructions and just about everything that I needed.
Good Luck guys.

 

All summer I got approximately 17 mpg. Sometimes more, sometimes less depending on the mood I was in that day/week. . Now that it is truly winter (got down in the single digits today) I'm looking at about 13-14. At least I believe it is the cold temps....any other suggestions? I change oil every 3-4k and fresh air filter 1 month ago....dont really see what else could change so quickly other than temp!

Greg

 

Umm Rod, thread is over a year old. But who cares, I get approx 15 around town and ooh 17 highway.
Mike

 

The blend of fuel used in the winter is thinner to help prevent gelling and is lower in caloric content and therefore cannot propel your truck as far per gallon.

 

Does anyone know if the cold weather will effect your MPG?

Eddie

 

It does, indirectly.

1st there is the winter blend fuel which has less energy value

and

2nd there is the exhaust backpressure valve that slows the turbo for a given amount of fuel, requirig you to press on the pedal more.

Also you might idle more to heat it up.

So, long story short, yes it will lower fuel milage, but the cold air itself does not do it.