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Old 02-09-2012, 08:19 PM   #9 (permalink)
slowmover
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Join Date: Oct 2009
Location: Fort Worth, Texas
Posts: 2,442

2004 CTD - '04 DODGE RAM 2500 SLT
Team Cummins
90 day: 19.36 mpg (US)
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I went through the way I see some of this in a thread on another site:

Fuel Mileage Upgrade [Power & Economy in Trailer Towing]

Note the info about perfecting hitch rigging. With that leverage set and verified on a certified three-pad weigh scale, then the "effect" in a manner of speaking, of the trailer acting upon the truck and visa-versa is brought to the lowest point.

If you'll go through the suggested points for work on the TT, etc, then all other comments/suggestions/changes will be magnified.

I would like to know about aero for the travel trailer. Should I install a belly pan? How is it done for the best aero efficiency. My T.T. is the typical brick in the wind. I do know my sweet spot is 58mph when towing. 12.5 - 14mpg. Any help will be appreciated.

TT [travel trailer] spec, just as with TV [tow vehicle] spec is the most important question.

The order of "knowing" vehicle expenses beforehand is relatively:

- Vehicle specification
- Climate
- Terrain
- Intended Use

Second, (a NeilBlanchard quote) has to do with vehicle spec,

the relative order of [mpg] importance is still:

* Drivetrain Efficiency
* Aerodynamic Drag
* Weight
* Rolling Efficiency

A non-aero trailer will always have a higher horsepower demand, and (importantly) never handle, brake or trail as well. So, once one has gone through and made ideal the mechanical baseline of both vehicles, solo and when hitched, one has reached a limit.

12.5-14 mpg isn't at all bad. Given that we here do not know at present the length of the trips, the terrain encountered, or over how many miles this figure is representative, it already looks good for what it is.

One might peruse the threads hereabouts in re big truck/trailer FE aero improvements. And, especially, orbywan with his Class C boat-tail build.

Moving to an aero trailer is the best change. Plenty of good used candidates. My towing mileage (sig) was in 105F degree Texas summer weather at 62+ mph. I imagine that I would have broken 16-mpg easily if I had slowed to my present 58-mph.

There are plenty of examples of CTD's pulling trailers of this type (most famously, Airstream) of from 28-34' in length, and from 8k to over 11k in weight averaging 14-16 mpg. The key is the overall average mpg. I estimate (as in the linked post) that a conservative number for me is 16-cpm solo, and 26-cpm towing, at todays prices ($3.79/gl).

Smaller A/S trailers (23' and under) being pulled by TD SUV's and sedans are seeing high teens easily, and there are a few examples in the mid-20's.

I also went through some of the same in a thread on this site:

Touring Musician

where the reduction of business expense was paramount, and, as one is both living and traveling in an RV, some of the same applies as a large context has to be considered, IMO, for total expenditures to make sense.

If one is full-timing in the TT, and covering a lot of miles then that would be a different approach from a combined rig that only travels a few weeks per year. Treat vehicles separately, and break out solo miles from towing miles to get an idea of just what the "towing penalty" really is on an annual and multi-year basis.

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Last edited by slowmover; 02-09-2012 at 08:58 PM..
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