Winter vs. Summer diesel
 

Along with a decrease in fuel mileage, power, ect, could that also lead to higher egt's when towing? While talking to a couple of fellow diesel owners, they said that could be part of the problem. I still have 3/8 tank of winter fuel in one of my tanks (I don't drive the truck much in the winter).

I've run into that while towing.

There is less energy in the winter blends so you need more fuel for a given amount of powahhhhh.