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Old 04-01-2012, 07:07 PM   #1
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Gas Mileage improvement, 25' to 22'??

I pull with a 2004 Ford 150 5.4 liter and currently get 9 to 12 mpg pulling a 25 footer AS. Any one know how much better it might be moving to say a 22 footer around 3200lbs instead of the 4300lbs I now pull?
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Old 04-01-2012, 07:46 PM   #2
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Hi, Billy,

And welcome to the forums!

Unfortunately I would not expect a measurable improvement in gas mileage in going to a slightly smaller trailer.

Our first Airstream was a 16 foot 1960 Pacer that weighed under 2,000 pounds. We towed it with a 1994 Chevy Silverado half-ton 4WD pickup with a 5.7 liter V-8. That truck got 19-20 MPG on the highway when not towing but dropped to about 10 MPG towing the little Pacer. Partly this was a matter of not using overdrive when towing but I think it's mostly a matter of air drag, not weight.

We later bought a 22 foot 1980 Caravelle that weighs about 4,000 pounds and there was no noticeable difference in mileage towing the larger trailer with the '94 truck.

(Of course mileage varies from time to time due to headwinds/tailwinds and hilly versus level terrain.)

Our current tow vehicle is a 2009 Chevy Silverado V-8 half ton 4WD. It gets about the same mileage not towing as the '94 (around 20 MPG), but 12 - 13 MPG towing on account of a smarter transmission and other tweaks.
.
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Old 04-01-2012, 08:08 PM   #3
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A rule of thumb is between 220 to 280lbs per trailer foot.. This does not count for personal items and major changes in construction between years..

Like Nuvite-7 stated above its not so much the weight as the mass.. I have a square box air plane trailer that empty is less than 1500 lbs.. Trust me on a windy day it pulls harder than my 27 foot Overlander fully loaded up with full tanks and ready to camp,..

With a semi truck,, we call it the roller coaster effect.. Charge down hill and let the flywheel effect help carry you up the next.. So in a way other than the wind drag,, weight can be of some help.. ( unless its a long hill)

Hauling dry fertilizer on back 2 lane roads where I can run my speed and not with traffic,,, I have gotten 10mpg on a 1100 mile round trip with 82,000 gross weight.. Average speed about 52 mph..

Rule 1 is never try to gain speed uphill..
Rule 2,, coast as much as possible to the point that brakes are not needed other than to kill the roll at the stop sign..
Rule 3,, pick roads with the needed wind protection makes a world of difference..
Rule 4 picks up rule 3 as night travel most times the wind is almost calm.. and the air is thicker for a better burn..

So you can see that bad habits cost a person more than a extra 5 foot worth of trailer.

Sodbust
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Old 04-01-2012, 08:48 PM   #4
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Fuel Economy Increase While Towing

For a given trailer shape the answer to your question is no. There will be a difference based on the drag of the longer trailer, and any weight increase will hurt acceleration as well as maintaining speed on a grade. But increasing or decreasing size won't, by itself, make much difference in mpg. There are at least a dozen of us with 28-34' aero aluminum trailers and Dodge CTD's seeing 13-16 mpg. The weight range is from 7k to 11k, yet the mpg is almost the same (where comparable terrain is factored).

The TV is the weak link (the most important determinant) when it comes to mpg gain or loss. Other vehicles might do better. But it must be weighed against the years, miles and nights spent aboard your TT.

Thus, assuming you will be making no changes in either TV or TT, then re-establishing best mechanical baseline is the first step towards better mpg. Start from scratch as if you just bought either:

On both TV & TT:

- Alignment
- No brake drag
- Tire pressure
- Hitch rigging per scale values (see CAT Scale thread). Best hitch rigging -- hitch design and ideal adjustments -- really do make a difference in mpg.

On TT:

- max sidewall tire pressure
- new shock absorbers (if so equipped; this is an issue in contention; search)
- bearing adjustment

On TV:

- No steering wander (from steering wheel all the way across FA)
- Best shocks and anti-roll bar bushings
- LT tires, closed-shoulder highway rib style in OEM size
- No lift kits or or other such
- Fluids & filters new
- All book maintenance to date
- Scangauge or Ultragauge
- Consideration of gearing and aero changes/additions

Each of the above is a subject worthy of some study. Nothing "obvious" in other words. Conduct a search on each, or ask.

I could not recommend sending money to strangers for magic gizmo boxes. Reports of mpg increase are almost never accompanied by depth of records to substantiate such. Payback must be figured. It may be quite a few years.

Prior to vacation: Plan fuel and other rest stops in advance in legs of about two hours or 100-miles. Be as rested at days end as at days beginning. Drive only in daylight. Keep glass immaculate. Whatever can be done to make the day easy & predictable is to the good in achieving best mpg. Fuel economy is really a lot of little things that, added up, give the edge time to increase. It's easy to lose it all by mistakes, misdirection, tension, etc.

Few are willing to plan. And use tools to make changes. But one can make substantial strides in trip planning. The big truck and big diesel engine manufacuturers will tell you that the difference between the best and worst professional driver is 33%. Assume then, you are the worst wanting to be the best and make changes accordingly.

Travel speed should be obvious. Anything above 60 mph is contraindicated. Horsepower demand doubles from 55 to 70 mph. The percentage change rises so rapidly as to offset any "gains" in travel time above 60, IOW. (And anyone who tells you they achieve better mpg at, say, 63 over 58 has a TV that is either mis-geared, or more likely, fitted with incorrect tire size. A change to that would reap them a better number, ironically).

Most of all keep accurate records. All miles and all gallons, year-round. The goal of FE improvement is in percentage increases to the average annual mpg. One can adjust ones solo driving to "create" fuel inside the same annual budget (fixed price). So records matter. As in my sig below I can calculate the cost per mile solo or towing. Or, that towing is about .66 of solo highway mpg. Etc. This is just another, deeper level of familiarity with ones vehicles.

I cut 2k miles off my average annual miles by combining solo trips and doing a better job of driving. Fewer miles more skilfully driven. This gave me several thousand miles of "free" trailer towing as the miles cut was combined with a 22% in average mpg. And no dimunition in quality of life. It's about reducing wear & tear, not just reducing fuel burn. When tires & brakes all last longer, that is also a form of economy that helps my recreational use of both vehicles.

Now, it is true that a smaller TT can be towed by a smaller TV. In that event the right choice can make for a substantial change in mpg. But all choices preclude others, and some high mpg TV's may not have other features to your taste.

.
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Old 04-01-2012, 08:54 PM   #5
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We went from a fairly light 29' to a heavy as 34' and only lost about 1 mpg.

Frontal area comes into play more than length or weight
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Old 04-01-2012, 09:23 PM   #6
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Frontal area comes into play more than length or weight

Strictly speaking, the shape of the frontal area (and of the trailers' end) is the key. Entry & Exit. In the same vein, trailer height is the killer for a trailer of a given shape. The usual flat front SOB sits too high off the ground and many of them are also quite tall as well.

If one were to "jack up" an A/S the mpg would drop noticeably. Maybe even dramatically in some instances. Darkspeed's raised A/S will not be achieving any high mpg numbers (if he re-substantiates in this physical dimension and finishes it).
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Old 04-01-2012, 09:44 PM   #7
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Ok gys thanks so much for all of that!
So then why would I wnat to change to a smaller one? Not sure now. Our 25ft is just right and our whole goal was to get better mpg. So maybe stick with what we have and do some fixin up.
Is there anything anone recomends to do to the truck other than what has been mentioned? I have the model that ford makes for towing. It pulls great with more than sufficient power. I guess there is always the diesel option but from what I ahve read one would have to drive alot of miles...like 50k to get back the money saved on fuel. I really feel like I have plenty of power so that need is not there. But I do know they get much better mpg but I would have to find a used on probably older than my 2004 ford to keep the price around 15k or so. The there is all the expense of maint. So any ideas that actully work for getting bette rmpg? I have flow master and KN filter on it already.
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Old 04-01-2012, 09:54 PM   #8
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Billy1,
I tow also with a Ford with the 5.4L and the trailer towing package. I average around 12 mpg towing a 19ft Bambi. I try to keep under 65 mph. I can run in overdrive most of the time on slightly rolling highways. A head wind will cut my mileage some. As a point of comparison, I only get about 15-16 mpg without the trailer. The rear end gearing helps in towing but keeps my mileage down with out a load.
Frank
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Old 04-01-2012, 09:56 PM   #9
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Post Try One Of These First

Quote:
Originally Posted by billy1 View Post
I pull with a 2004 Ford 150 5.4 liter and currently get 9 to 12 mpg pulling a 25 footer AS. Any one know how much better it might be moving to say a 22 footer around 3200lbs instead of the 4300lbs I now pull?
I had great increase in fuel mileage with an roof mounted air deflector when we pulled a 28 footer up to Nova Scotia and back, sometimes twice a summer for vacation. It paid for itself in fuel savings on one round trip, ball park, 1800 miles!

Side note; Here in Texas, the April bugs are out! They call them June bugs up north! ... Well, don't ya know that this deflector also keeps them critters and others from embedding themselves all over the front of your trailer! Much less elbow grease, used to clean!
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Old 04-01-2012, 10:01 PM   #10
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How much did your MPG increase?
How much do they cost? I wonder if you are pulling an AS? I wonder if it owuld make as much difference because of the rounded shape of the AS?
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Old 04-01-2012, 10:23 PM   #11
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Hey, billy1

The best TV is going to have a turbodiesel. No way around it. But you are right that one must be able to cover the cost of more expensive fuel with mpg that is high enough to offset that difference.

A few years back I made a comparison of my truck against a man with the same truck and trailer, but his had the gas engine. Over quite a few categories we compared notes. What we came up with was this: so long as diesel was no more than 50-cents per gallon higher in cost the other numbers were a wash. It really did come down to how much longer the diesel engine lasted over the gas motor. That is, that the diesel would still be working hard at 250k when the gasser would be expected to be tired.

Of course the diesel could already "outwork" the gas motor. But we're comparing pretty much the same trailer and solo miles. Both of us lived in cities and the trucks were our DD's otherwise (and had business use, too).

So, on any truck it comes down to:

Truck spec
Climate
Terrain
Use

Inside of truck spec are:

Manual or auto transmission
2WD or 4WD
Highway rib or traction tires
Turbodiesel or gasoline

where the first is the better choice. Now, if a diesel is to your liking (and is otherwise justified where high mpg is the best choice; i.e., no 4WD) then trucks from 2007 or earlier (no Fords) are the best choice. The spec of my truck (signature) was no accident. It was chosen specifically for

Longest life at lowest cost with highest reliablity.

In 180k miles I've spent $45 on repairs, and tires/brakes last above 120k , etc, (and I am not alone with this, on this year/engine model).

But, as with some others, I also have some IRS miles annually for business that helps. A 1T truck is no easy thing to drive around as is a half-ton. So be careful about this kind of choice if it doesn't fit with DD chores. Sacrifices made for towing mpg are about as smart as lift kits & offroad tires on a 4WD that is mainly used for runs to the beer store.

How many miles do you tow annually?

How many nights/year are you aboard the TT?

How many years/miles will the TV be in your possession?

These are the important questions to answer for yourself -- not fuel mileage -- since depreciation, finance, insurance, maintenance and repairs are the fixed costs that really determine economy. Economy with a capital "E" as fuel mileage is smallcase "e" in comparison.

I see that your reported towing mileage varies by 25%. Is that accidental or . . ? The use of cruise control is recommended by big truck/engine manufacturers as one of those factors distinguishing good from bad drivers. Mine is on before the end of the highway entrance ramp. I may kick it out for the hills, rain or traffic, but it is a proven method of consistent mileage.

Until one can predict -- closely -- what the mpg will be for a given trip, then attention to consistency needs to be paid. Experience counts, but the miles are wasted in learning without records and notes. Mpg really is about skill once past the factors above. That skill is mainly in paying attention to what, where and how over time. And making changes that records reflect accurately.

As ol' Ram Dass had it: Be Here, Now

.
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Old 04-01-2012, 10:25 PM   #12
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I can't add much to Rednax' post. Lots of good in that.

Perhaps the 22 is a bit narrower and lighter, and would give a slight mpg improvement (half to 1 mpg). But to me it wouldn't be enough to warrant the cost of the trade.

I'll repeat a few things, keep it 60 or under, tires inflated properly, morning drive if possible (wind tends to be lighter from dawn to mid day in many areas and the only good wind is a tailwind), look at total economy of towing and non travel driving, scan gauge, rebate credit/gas cards, consider fuel economy when vehicle purchase is necessary, both tow vehicle and other vehicles.

Also I have observed some indication there is a slight benefit from following another RV or big rig. NOT at tailgating or dangerous distance, but a normal following distance, provided they're at appropriate speed.
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Old 04-01-2012, 10:38 PM   #13
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Gas Mileage improvement, 25' to 22'??

Greetings billy1!

Quote:
Originally Posted by billy1 View Post
So then why would I wnat to change to a smaller one? Not sure now. Our 25ft is just right and our whole goal was to get better mpg. So maybe stick with what we have and do some fixin up.
I would be surprised if the proposed change in Airstream sizes would make a huge difference in your towing fuel economy. My experience is with Vintage Airstreams, but I do have a 1964 Overlander that is 26' 8" with a loaded weight of 6,100 pounds as well as a 1978 Argosy Minuet 6.0 Metre that is approximately 19' 9" with a loaded weight of 3,200 pounds. Since both coaches are well below the maximum 10,000 pound trailer tow rating of my K2500 Suburban, I am able to tow either coach in Overdrive - - - towing MPG with the Overlander is 11 MPG while the towing MPG with the Minuet is 12 MPG (can push 13 MPG on flat interstates). The Suburban is pushing 200,000 miles with over 75% of those miles towing one of my coaches.

I do notice a much more pronounced MPG difference when comparing MPG performace of my '75 Eldorado Convertible. It has the very powerful 8.2 Liter V8, but is hindered by the 2.70 final drive. With the Eldorado, my towing MPG with the Minuet is 8 MPG while its MPG when towing the Overlander varies between 6 and 7 MPG. The Eldorado is doing very well when it averages 12 to 15 MPG solo.

Kevin
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Old 04-01-2012, 10:43 PM   #14
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We went from 20' to 25' Airstream with no difference in mileage with our 4.7 Tundra.

Think about it this way. Even though we are now pulling 1200# more, the total difference is not that much. You have consider the overall weight, truck, trailer, gear, and people. Only the empty trailer weight changes.

The greatest factor, wind resistance, is still virtually the same as well, and that can easily be improved by simply lowering speed.

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