Seems to me that back when I was in Florida, I was getting 18mpg or so on the highway according to the trip computer. Now I am in Upstate NY and thing shows 14 MPG. Im running clean filters and everything. Is either the fuel or something wrong with my truck. I got a 2001 2500 Cummins H.O. 6-speed manual. Where else can I check for better MPGs?

I'm finding the same thing with my '04.5 CTD and I found the same thing with my old '97 6.5. Winter + cold temps = worse mileage.

Of course, right now I'm getting about 18-20 mpg @ 70 mph empty, and it's cold. This makes me happy. I wonder what summer will bring! :)

Winterized fuel has less BTU's per gallon.

The trucks burn a little more fuel to keep warm. Gas motors do the same thing. I also find that I leave mine idling a lot more over winter...this works against you fuel mileage a lot!!!