New to this forum.......... I guess from what I have been reading in various forums, that the fuel mileage I am getting from my 05 f350 power stroke with 4:10 rear ends is about right. I didn't buy the truck for fuel mileage, but it sure would help if it was a little bit better. Is there anything that I can do, to increase fuel mileage, without voiding my warranty? It has 38,000 miles on it now. That fuel mileage is mixed highway and city, not towing anything, nor hauling anything in the bed. Dealership told me it would get around 18-20mpg, They'll tell you anything to sell a truck..
I am now 50 and this is the first pickup I have ever owned, always said, " if I bought a pickup it would be a crew cab dually ". so i got what I wanted.

 

Without voiding the warranty is a tough call. As that is the discretion of the dealer.

Anyways, there are a few things you can do. My father in law has done some work to his, but this is a 90's truck but in general it is the same. Look at a better exhaust system, a Cold Air Intake also seen as CAI. And get a tuner. I know for diesel engines you can get a tuner that can give you a conservative tune that will getyou better MPG's and with the deisel engines you can adjust on the fly to a tune that will give you better towing capability or give you more HP's to go fast.

Look up bullydog for a tuner and find their website for a better explanation. There are others out there as well but don't know ones that are diesel engines.

 

Try www.thedieselstop.com, and try a set of 3.73s for the axles, with a diesel, you don't need 4.10s, like you would on a gasser, there's plenty of low end grunt to overcome the slightly taller gearing. Maybe a change in you tire width andheight would help.

 

I had a 2007 4500 solved the problem could not handle that 8 mpg so I sold it and got a 2011 power stroke that Gmc was a diesel. My power stroke gets 21 to 24 mpg. I just got me another f250 ford 2012 and all miles in town got 15 mpg and the second tank got 15.5 mpg out in open road I am thinking 20 to 23 mpg
This is a lot of idling while my wife shopped. I am very pleased.