Looking for Insight

[Geek's 65]

Before I go waltzing in to the dealer with this, thought I would ask for some of the experience here. I have a 2012 F250 FX4 and for the first 2543 miles it was awesome. I could easily get 18 mpg average (lots of 19 and change if I was on the freeway and unloaded - that's calculated and on the computer) with power out the wazoo. Then it's like someone flipped a switch. All at the same time I got:
Mileage of 16 - 17 mpg IF I was very nice to it
NO real get up and go (passing a car and asking the truck to go from 50 to 80 used to be a non-event. Snap your head back. Now I put in reservations.
A noticeable ticking/clicking when the truck idles after it warms up
A lot of different noises after the truck is warm and I shut down.

I should also note that the boost says I am still getting 10 to 20 depending on how hard I push the pedal but my butt says it's not really there.

Anyone have a similar experience and know what was done to correct it? Not new to mechanical stuff but am new to diesel so I don't want to show up TOTALLY ignorant when I take it in.

Thanks ahead of time.

Geek

[BadDogPSD]

Not sure what part of the country you're in, but winter blend fuel can have a negative effect on both fuel economy and performance.

Have you drained your fuel bowl?

[Geek's 65]

Yup. Fuel bowl has been drained. Good to know about the difference in diesel for winter. Knew we did it with gas but didn't know diesel. I did mention I am new to this right? I have been using Optilube as a cetane booster and such. Looked at the instructions and they indicate a higher mixture if it gets below 32 (0C). Being in SOCAL it doesn't get that cold but I did fill up again today and picked a mixture between "normal" and cold to see if it would help.

G