I just bought my 08 f-350 KR a few months ago. The meter was always around 18mpg, I hand calculated to about that as well. Last month I had my filters and oil changed. Ever since then, my mileage has been dropping. No matter how conservative I drive, it keeps dropping. It's now at 16.1-16.2. I would assume next week it will be less at this rate. I brought it to a mechanic and he claims absolutely nothing is wrong. I have 160k on it now. The truck has been deleted with straight pipes and tuned with an XRT pro by H&S.

I have not changed the tune or anything since I bought the truck. I am always under 2000 rpm..

Bottom line- ever since the oil and filters were changed, mpg has been dropping.

Any input would be greatly appreciated.

Thanks!

 

Have you reset the liometer lately, it works on an average so I would reset it and see what happens.

 

One thing to consider is that you are now burning winterized fuel. Sept. to Oct is when refineries start the change over to improve cold weather usage. Unfortunately, we all pay the price due to this. Northern states get changed over first then it typically trickles to the lower states.

 

Yep winter fuel and colder weather.........

 

I'd blame the winterized diesel too, make sure you run some sort of additive to compensate though. (Stanadyne, Diesel Kleen, etc) I've been running AR6200, it's Archoil's fuel catalyst that makes the helps the fuel burn better and have more energy. Yeah, it sounds like snake oil, but even on winter fuel, my 6.0 Excursion is getting 15-16 mpg easily where it used to get 14 mpg (with me babying it) or so during the winter.