[slowmover]

Welcome

There are several CTD owners here. Search posts under Cummins. Also on CF. Search posts under my name.

Here the outline:

MPG is part of vehicle operational cost. Using a journal or phone app, record all miles and all gallons purchased. At the end of a specified period, quarterly or annually, total miles divid d by total gallons will give the important number: the average.

Tank by tank doesn't mean much. Subject to all sorts of error

The trick to reducing fuel consumption is to get the most from each gallon. This is primarily operator mindfulness. The desire to become a better driver.

Modifying the truck from stock configuration isn't the answer (I'm not going to comment on emissions deletes). The truck as delivered new is best.

Reduce the number of annual miles, but get the same things done.
Combine multiple trips into one.
Eliminate idling
Drive so as to never stop
No left turns
Etc.

Start with records and start by getting the engine hours recorded on the truck. Divided into odometer miles, this will give the average mph. The higher this average, overall, the higher the MPG. Below 27-mph is unacceptable. Cummins rates engine life at 35-mph.

The goal is an increase to the average annual mph and a PERCENTAGE improvement to the annual average MPG

The way to do that is to reduce the annual number of miles while accomplishing the same things AND to drive the remainig miles at a higher level of skill.

Okay.

Skill enhancement is what you're asking specifically. On different year models things will vary. For best economy I upshift the NV56 in my truck at 15-1600 rpm. I avoid ever getting above 2000 rpm in any scenario. Etc. This means quite a few details to work out so as to never have to stop in city traffic. Different times. Different routes. Different speed most of all.

Same for highway. Aero resistance shoots sharply up at 60-mph. I run 58-mph. I plan any stops in advance. I drive pretty much the same way solo or towing my 35' travel trailer.

Another gauge of keeping money under control is brake and tire life. I average over 100k on those two.

Take it for granted that long life, fuel economy and safety are all on the same page.

Spending money on gizmos, etc may never pay for themselves. Work that out in advance.

Keep records and be willing to establish new habits. 13-weeks of being consistent for a new Pattern.

Lots more here. Much in the how to. Details.

Diesel Dave set some records. Read what he did. But remember the highlighted above. Right attitude and good habits. Don't start something you won't use every day. But push to find out what you will.