Yea that's what I was thinking, good thing I never passed a cop.

Posted a couple of pics of the filter on the fuel rail, I couldn't tell that it was dirty. Really simple job, didn't take but about 10 minutes.

 

I have yet to remove a primary filter on this truck that was what I would consider dirty. The primary on my 6.0 was always obviously dirty, but my fueling situation improved prior to the arrival of the 6.7. You said your secondary filter was more difficult to blow through than the new filter. Once you soak that new filter with fuel, it too will be more difficult to blow through. A saturated filter is a whole different game than a dry filter. If the secondary is getting plugged up, you either have an ill fitting primary filter or it has been compromised.

 

Hard to tell on the close up pic but the other looked fine. I think it is best to start with a fresh set regardless since you just bought the truck.

these newer fuel systems will not tolerate any water.

I think you have also narrowed it down to a tire change size throwing everything off.

 

Your right I think the secondary filter was fine

 

I think it's a combination, of the 3.31's with the weight I carry plus the tire size is the perfect storm for poor mileage. Plus I also let it idle, which has never been a problem in the past.

I would like to think everyone that chimed in and helped me, I'm glad I decided to join the forum.

Thanks
Kris

 

Stock speedometers read about 2 mph faster than you are actually going in my experience.

 

did you try to do the relearn process as well. That is about the only other item I had mentioned that you could try.

May or may not help.

 

Yes I did the relearn when I changed the filters. I'll let you guys know if it helps, I don't drive a lot of miles everyday so it will take sometime to see if we've made an improvement.

 

Its funny that nobody is talking about checking the air filter.
My fuel economy improved almost 1 mpg by installing a clean air filter. My truck had 25k miles on it and the air filter was almost completely black and plugged up. A new one even improved the power levels. Make sure you remove the air filter and inspect it, as the plunger doesnt actually work. Mine showed fine, but air filter was disgusting.

 

I owned a 2011 Superduty 6.7L and it had stock 17 inch wheels and tires....I upgraded to a set of Ford 20 inch wheels and 275 / 65 / 20 tires....running 65 lbs of air. Have the speedo reset to 18 inch wheels and 295 / 65 / 18 tires....do not try to reset the speedo to 20 inch wheels and tire....with 3:31 gears.....it can't be done.

 

My mileage drops rapidly for any speeds over 70 mph. The faster I go, the worse the mileage. I drive how I feel like driving and don't worry about how much it's going to cost me when I fill up, but trying to increase my mileage is a game for me sometimes. I'm all stock with mostly highway miles. I average 1 regen per tank and I typically see 16 mpg per tank. If I bump my speeds up, I'll drop to 14 mpg. I've experimented with certain driving styles over the course of entire tanks.

 

I can also confirm it cannot be done. Mine is still at the default setting.
I stood with the tech for at least 20 minutes while the tech tried several options within IDS but everything he did, other than default, would throw a CEL.
What wheels/tires have to do with the engine is beyond me!

 

It has a cold air intake on it so the filter is visible, it looks clean. That's prolly why no one has brought it up.

 

I was driving a 6.0 Chevy single cab before I got this diesel, and it got 10 mpg, no matter how you drove it. Baby it around or drive it like you stole it. My father has always drove the diesels but every time I'd pull a trailer I'd use one of his diesels because it was just really nice to pull with. So I've never really changed my driving habits while driving until this truck. I don't drive hard by any means but I don't run around at 45mph all day. If I'd quit looking at the average mpg on the display I prolly wouldn't care.

My old truck was easy, trip set at the gas pump would say 230 miles you'd put 23 gallons in.