[slowmover]

We are open to going to a lower trailer such as an Airstream. I have a sort of goal of a diesel truck and fairly roomy trailer combo that allows 15 MPG.

I've collected about a half-dozen to dozen stories of Dodge CTD's pulling either Airstream, Avion or Silver Streak trailers of 28'-34' (7k-11k GVWR) where the mpg range is 13-16. So far as I know, none were "serious" about fuel mileage (beyond a good choice of TT & TV which is the most important spec for FE). At least one of a Duramax owner (earliest model engine) where mpg was also in this range.

As to what "boxes" may work best on a DM, you'll have to tell us.

On the "new" 5'er: Taller is a huge problem. Aero resistance means more than weight, especially in steady-state cruise.

winter fuel

There is a recent thread on this subject on this site, and a current one about the relation of temps & mpg. Temps far outweigh "winter fuel" as a source of decreased mpg.

"Average speed" is sort of like "average mpg". Depending on truck use a higher number is indicative of good practice (to a point). Low average speeds (over the life of the truck, or on a calendar quarterly basis, etc) will show lower mpg and are indicative of extended idling (sub-25 mph, usually). Average speeds of 30-35 mph (and higher) appear to be "good" for both long life, few problems and best mpg.

EDIT: Okay, I found RTH's posts. Not a lot of information in general, nor about any DM specifics beyond a brand name tuner. Maybe a PM to him will generate a response (been two years since he last posted).

I see in an owners poll on DieselPlace that LLY's are mainly in the 15/17 mpg range town/country. The poll isn't broken out for 4WD/2WD or for manual/automatic transmissions. These numbers aren't substantially different than for CTD's; the prevalence of 4WD/Auto spec and ******* highway/dirt tires keeps them with an average of around 15-16 mpg.

As best I can tell, even on a CTD, the addition of a tuner called a Smarty Jr and a camshaft change (on some years) might be worth 2-mpg averaged. The "action" is with proper tires, gear changes and some aero help when it comes to spending money to try to save money. That's still a short expensive road compared to driver awareness improvement (skill acquisition).

EFI-Live holds more promise (software) but I'm not aware of men who are programming "tunes" for economy (a problem of demand). Engine cylinder pressure is the key, but not too much. Any tuning that involves adding fuel by duration or pressure is the wrong direction so far as I can tell.

My own order for what is important is [1] longevity, [2] reliability and then [3] economy. FE is a way of gauging how well the rest is going. So longest brake & tire life, for example, are indicative of best operating practice. Less than 70k on either of those would be indicative of the need for some driver training. Etc. (More than one way to come at economy is the point).


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