F 250 Diesel Fuel Mileage Issues Need Feedback?

I have a 2004 F 250 Diesel four Door Super Cab. For the 1st six months after we bought it, the car was to get 18mpg. Then all of a sudden the fuel mileage dropped to around 13mpg. I have gone back to the Dealer and talked to Ford, but nobody was able to satisfactorily answer my question or supply me with a solution.

They just tell me that since Ford isn't obliged to put the mileage ranking on the sticker, there's no ensure of a mileage range so just it is tough luck.

I am trying to learn if anybody else experienced this and if have they found a solution? I tried a SuperChips re programmer and it helped a little, but it still isn't near what it was firstly.

4 days ago
To answer some of the questions, I have had Ford check the engine completely and they say all systems are working properly both times, and I change all fluids and filters as indicated by the maintenance schedule, and nobody but a Ford Dealer touched the car. as well, I'm using a chip programmer, so the factory chip is still in the car. I can program it for three different scenarios: Economy, Towing and Performance. Of course I use Economy most of the time.

The oil businesses have change to the low sulfer fuel and its effecting the mileage I went thu it attempt running a bottle of marvel mystery oil when filling up and see if that change the mileage.
Some people are running snowmachine two cycle oil and its working for them.
Another problem which you may see is small fuel leaks which there isn't much you may be able to do about it, the new fuel is thinner and in some of the older engines it a real issue.
On the lighter side come winter it'll start a lot easeir and the is no more winter fuel, I had no problem last winter here in Alaska.

Do you know if the turbocharger is functioning correctly?

Check out your air filter, oil, and transmission liquid also.

that's easy you been using the new bio diesel

check your air filter, the fuel filters can be dirty, the cat can be clogged. is there a obvious loss of power? may be the famous injector problems.

I would not use after market chips..very bad for your truck. Your fuel mileage will differ till your motor is worn in around 150,000 miles . Mine is just below that and the more I drive it the better my fuel mileage was to get. Also are you doing lots of short trips? That will really kill Fuel mileage on a diesel. Have you been keeping your oil changes and filters clean and up to date? That will also effect your fuel mileage. Watch the fuel you're putting into your truck also. Some stations use bio combinations which do not get as good of fuel mileage.

You mat have a leaking injector that lets a bit too much fuel on each stroke or a leak in the fuel supply system.

Temperature, grade of diesel fuel, how you calculated the mileage that you were to get in the beginning are all going to change fuel economy. it's true the the truck doesn't have any fuel economy ranking because it's over 8500 GVW.

I could check your economy after your next oil change and have put 1000 miles on the new oil. attempt to drive the same way you generally do and monitor the mileage.

13 mpg does not sound that bad for a 250 SD

Don't know lots about the problem but I could check the fuel filter, check for possible leaks, and see if the fuel changed ie, cheaper grade different mixture and soforth. Have your driving behavior changed?

Ok other than the programmer those things can screw up systems too. had too many programmers and chips cost their holders money on a p stroke caused by this .. are their any other mods to the truck at all? Most like to get the custom exhaust that is why I am asking.

I could asked if it was after a visit to the dealer if not using a programmer as Ford had many strange recalls for the 6.0s dealing with the idle on those trucks. and most involved reprogramming three modules remember your power programmer only fools the truck .. Possibly the reprogram did something.. can be wise to see if the program changed again from your Ford guys and run the new for a while and see.

Other than that, Have to see the truck to get more ideas. do not usually do P stroke work, but those two are the things we see lots of ...

I agree with Jim W, its the new Bio Diesel. If something, like your turbocharger messed up, the diagnostic report on your computer could poped up the "Service Engine Soon" light. All Fords are computerized man.

As with all diesels, its all about the fuel. Any variation in fuel structure or quality can have an effect on the fuel economy. but, I agree with the opinion that mileage can differ in a car that is not "worn in".