Reply
 
Thread Tools Search this Thread Display Modes
 
Old 09-16-2012, 10:53 AM   #1
Rivet Master
 
mstephens's Avatar
 
2013 25' Flying Cloud
Cat City , California
Join Date: Sep 2012
Posts: 854
15 MPG Pulling a FC 25!

Well, that's what I want! As much as I love my Suburban, I am not in love with 10.6 MPG. If gas goes to $5, I'll have to anchor my Flying Cloud to a tree.

Is anyone getting that kind of mileage towing a 25er? I hear about Toureg and Ecoboosters, but I see more like 12 MPG'ish figures. I don't want to invest a lot of precious capital in a new TV to get 1.5 more MPG.

I wonder if my internal standard for what it takes to two a 25 is just too high? I am intrigued that in non-USA places the TVs seem much smaller, lighter and efficient. Are we "over-towing"? I have 320HP and 4:10 gears. Is that really necessary for a 25?

Oh please - - I am not looking for an "unsafe ride." Don't mistake my quest. I am not trying to overload axles, or brakes or any of the other no-no's we all get scolded for. I am just wondering is there is some "un-conventional wisdom" about towing that I am unaware of? Maybe we are just "muscling up" too high based on the old adage that "we've always done it this way." When I am at rally's I see 25 and 28 footers being pulled by essentially "monster trucks" - gigantic 1 tonners with huge diesels and such. Seems a bit much at times.

Man, I'd love to 30% or 40% better gas mileage! (If I could)
__________________

__________________
mstephens is offline   Reply With Quote
Old 09-16-2012, 11:18 AM   #2
Rivet Master
 
SteveH's Avatar
 
2005 39' Land Yacht 390 XL 396
Common Sense , Texas
Join Date: Sep 2007
Posts: 5,311
I read once you could improve fuel mileage by adding acetone to your fuel, and when I asked an old mechanic friend about this, he said, "wanna burn less fuel? Stay home!"

The sad fact of the matter is, it takes a certain amount of energy to move a certain amount of mass with a certain amount of wind resistance down the road. So, you can reduce the mass, and/or reduce the wind resistance, but both involve leaving the trailer at home.

You can drive slower, and I believe you'd have to go down to 30-40 MPH to make much difference, but who amoung us is willing to do that? Europeans drive more fuel efficent vehicles (they don't have an EPA), tow lighter trailers, and tow them slower. (they don't have as far to go)
__________________

__________________
SteveH is offline   Reply With Quote
Old 09-16-2012, 11:38 AM   #3
Rivet Master
 
mstephens's Avatar
 
2013 25' Flying Cloud
Cat City , California
Join Date: Sep 2012
Posts: 854
Quote:
Originally Posted by SteveH View Post
The sad fact of the matter is, it takes a certain amount of energy to move a certain amount of mass with a certain amount of wind resistance down the road. So, you can reduce the mass, and/or reduce the wind resistance, but both involve leaving the trailer at home.
Absolutely right. What I am wondering though is if I am wasting energy by having more than I need to move that mass, with that wind resistance down the road. Just as a hypothetical, if my trailer needs 80 HP to move it and a TV at 55 MPH, should I get that 80 HP from a 350 HP motor, or a 200HP motor? Am I overpowering the problem, in other words? Is this an efficiency issue?

Maybe it could be stated like this. Suppose one were to design a TV based on these goals:
- 25 FC
- Cruise at 60 MPH
- Climb grades at 50 MPH (or "safe speed" let's say)
- Get 15 MPG over all

Would that vehicle look like a V8 gas 320HP SUV? Or, would it look like something different? Would it even be possible? Just a thought exercise.

Here's a kind of related interesting discussion about how much horsepower you need. *CelloMom on Cars: How much horsepower do you need?

Food for thought.
__________________
mstephens is offline   Reply With Quote
Old 09-16-2012, 11:46 AM   #4
Rivet Master
 
SteveH's Avatar
 
2005 39' Land Yacht 390 XL 396
Common Sense , Texas
Join Date: Sep 2007
Posts: 5,311
Surveys of people pulling a given sized trailers with smaller engine vehicles, like 3.5 to 4L, and traveling the same roads and speeds as those with larger engine vehicles, tend to get even worse fuel mileage.

The key in my opinion is speed, resistance to movement thru the air, and weight.
__________________
SteveH is offline   Reply With Quote
Old 09-16-2012, 11:47 AM   #5
Old School Young Gun
 
ElCamino Man's Avatar
 
Currently Looking...
Olney , Illinois
Join Date: Aug 2012
Posts: 382
The ONLY vehicles iv heard of getting decent mpgs while pulling a trailer had diesel engines in them. Theres really no compromise to that. The new EcoBoost is the hottest thing on the market: 8 cylinder power, 6 cylinder economy. But they still only get 12ish towing and its still a $30,000 truck used.

The only way I see getting good mileage when towing is using a car to tow it. Id never trust it but theres quite a few people on here doing it with excellent results.

You guys are geeting in deep with this intertia and wind resistance and power to pull stuff lol. If you say you need 80 hp to "move" your trailer, then use a classic VW Beetle to pull it lol. Just dont expect to go up a hill or win any land speed records. You dont NEED 300 hp to pull a trailer that needs 80 hp to move it, but you gotta take into account that the extra hp keeps you moving when your there, hence the reason diesel trucks make crazy horsepower and torque numbers. Especially torque. Gets you up to speed quick, retain your speed while your there, and have enough power left over to lug it up a hill without revving into the stratosphere
__________________
No Airstream Yet...
ElCamino Man is offline   Reply With Quote
Old 09-16-2012, 11:52 AM   #6
Rivet Master
 
2002 19' Bambi
Lafayette , California
Join Date: May 2005
Posts: 707
I am not sure what the absolute maximum horsepower in the towing vehicle has to do with towing mileage. We now tow our 19' Bambi with a 2011 Jeep Grand Cherokee and formerly towed it with a 2006 Grand Cherokee. Both tow vehicles have/had the 5.7 l Hemi V-8. The 2011 is heavier, larger and gets about 25-30% better gas mileage while towing the same trailer. That does not get us up to 15 miles per gallon, but over moderate terrain with little to no wind and towing at 65 mph, we have gotten better than 14 mpg.

Ignoring hills and wind, the greatest influences external to the towing vehicle are the frontal area of the trailer and the towing speed. The round shape of an Airstream helps, of course, but that effect remains the same if all you do is change the towing vehicle.

Tim
__________________
Tim A. is offline   Reply With Quote
Old 09-16-2012, 11:57 AM   #7
Rivet Master
 
1988 25' Excella
1987 32' Excella
Knoxville , Tennessee
Join Date: Oct 2010
Posts: 2,163
Blog Entries: 1
I get 15 mpg towing my 25' Excella. It is a '88 model and has a gross weight of 6800. We do not run it that heavy. I use a little 6 cyl engine and an automatic transmission. (5.9 Cummins). Before that I towed it with my 4.6 liter F150. I got 9 mpg and could not go very fast uphill.
__________________
Bill M. is offline   Reply With Quote
Old 09-16-2012, 12:15 PM   #8
Rivet Master
 
dkottum's Avatar
 
2012 25' Flying Cloud
Battle Lake , Minnesota
Join Date: Jun 2009
Posts: 7,716
15 mpg diesel is not equal to 15 mpg gas. Costs more, not to mention purchase, servicing, repair prices.

doug k
__________________
dkottum is offline   Reply With Quote
Old 09-16-2012, 12:27 PM   #9
Rivet Master
 
1988 25' Excella
1987 32' Excella
Knoxville , Tennessee
Join Date: Oct 2010
Posts: 2,163
Blog Entries: 1
Gas not specified in the OP. Just 15 mpg. One way to get higher mpg towing is to increase engine effeciency when under load. That costs a bit one way or another, so thats why we have big gas engines and low gear ratios as an alternative. Driving slower might be another alternative. Have seen references to direct injection gas engines. I doubt that is gonna be cheap either.

My older diesel has 2 things going for it a gas engine does not: lax on pollution controls and the higher compression ratio. The newer diesels are not quite as lax on pollution so that lowers their mpg a little.
__________________
Bill M. is offline   Reply With Quote
Old 09-16-2012, 12:42 PM   #10
Rivet Master
 
2005 19' Safari
GLENDALE , AZ
Join Date: Aug 2004
Posts: 2,441
Two things that affect fuel economy that are within your control and don't cost anything, are tire inflation and cruise speed. Try these tips on your next outing, and see if you notice any difference:

* Inflate Airstream tires to maximum pressure printed on sidewalls, if you do not already do this.

* On your Suburban, depending on load conditions and present inflation pressures (do not lower pressure if you already exceed these values), for LT tires (load range D and E), inflate tires to 55-65 psi (55 psi, minimum). If you are already using higher inflation values (e.g., for tires rated at 80 psi max), add 5 psi to your present pressure; but do not exceed maximum printed on sidewalls). For P-rated (passenger) tires, inflate to maximum pressure on sidewalls (typically 44 psi).

Note: Check trailer and TV tire pressures when cold; and if pressures exceed the maximum printed on the sidewalls after they heat up, DO NOT LET AIR OUT! Tire manufacturers know that pressure increases as tires heat up, and your tires are designed for this slight increase/overage.

* Wind resistance increases exponentially with speed, and fuel consumption at 75 mph is drastically higher than at 65. If you normally cruise at 65, 55 will also result in significant savings. On the highway, set cruise control to 55 mph maximum (or lower, depending on posted speed limit). The goal is to cruise around 2-3 mph slower than other traffic (except semi's), so that nearly all traffic is going the same speed or faster than you are; and you are NOT passing any other vehicles, except those bogged down on long grades. To maximize fuel economy, do NOT exceed 55 mph.

* Keep your foot off of the accelerator AND the brake, as much as possible. Resist the urge to pass vehicles in front of you, if they are going a reasonable speed. In addition, allow your vehicle to coast when slowing; and minimize brake use. Every time you push on either the accelerator or brake pedal, you are dumping gas and money down the drain. Your cruise control computer is smarter than your right foot when trying to maximize fuel economy.

* If necessary, slow a couple of mph to stay behind traffic, or pass using the accelerator as lightly as possible. If you are passing more than a few vehicles per hour, you are going too fast. The goal is to stay on cruise control as much as possible, and not exceed 55 mph.

I would be surprised it you don't get a couple more mpg out of your existing TV.

Also, despite the few extra dollars spent at the pump when fuel prices go up, that amount is far exceeded by new car payments and higher insurance premiums on a new vehicle. You probably researched your TV thoroughly before buying and justified the purchase in your own mind. Nothing has changed except your perception, which is influenced by a couple of extra dollars spent on each fill-up. If that bothers you, try buying your coffee for the morning commute at McDonalds instead of Starbucks (it's actually pretty good).

Please post your results, as I'd like to see if this helped you as much as it did me.

Good luck!
__________________
Phoenix is offline   Reply With Quote
Old 09-16-2012, 12:50 PM   #11
Rivet Master
 
Denis4x4's Avatar
 
2006 25' Safari FB SE
Currently Looking...
Durango , Colorado
Join Date: Feb 2006
Posts: 1,111
When the California Air Resources Board (CARB) was formed in the 1960's to combat smog causing emissions, it led to the inclusion of eco-politics. That has cost the American vehicle buyer tens of thousands of dollars to please a voter block that is selfish and could care less about people outside their elite circle.

So far this year, it has cost me almost $3500 to repair the damage ethanol has caused to my boat and collector cars.

Two things a man lies about his his sexual prowess and gas mileage!
__________________
Denis4x4 is offline   Reply With Quote
Old 09-16-2012, 12:58 PM   #12
Rivet Master
 
1974 Argosy 20
2014 20' Flying Cloud
Kooskia , Idaho
Join Date: Jul 2009
Posts: 4,591
I have towed the same 20' '74 Argosy, 4200#, with a Jeep Grand Cherokee straight 6, 190 hp, a Jeep Grand Cherokee V8, 270 hp + or - (can't recall) and now a Jeep Grand Cherokee with the hulking Hemi V8, around 380 hp. Same areas, same trailer, same driver, same patterns of use. In each rig my milage has been, by actual measurement over long time periods, 13.5 mpg.

So, no, it is not the hulking engines that are doing it. Overall mechanical resistance and aerodynamics would be my guess. BTW, the latest Grand Cherokee gained 1000 # over the old ones. Same milage however.
__________________
idroba is offline   Reply With Quote
Old 09-16-2012, 01:10 PM   #13
Rivet Master
 
mstephens's Avatar
 
2013 25' Flying Cloud
Cat City , California
Join Date: Sep 2012
Posts: 854
Quote:
Originally Posted by Phoenix View Post
Two things that affect fuel economy that are within your control and don't cost anything, are tire inflation and cruise speed. Try these tips on your next outing, and see if you notice any difference:

* Inflate Airstream tires to maximum pressure printed on sidewalls, if you do not already do this.

* On your Suburban, depending on load conditions and present inflation pressures (do not lower pressure if you already exceed these values), for LT tires (load range D and E), inflate tires to 55-65 psi (55 psi, minimum). If you are already using higher inflation values (e.g., for tires rated at 80 psi max), add 5 psi to your present pressure; but do not exceed maximum printed on sidewalls). For P-rated (passenger) tires, inflate to maximum pressure on sidewalls (typically 44 psi).

Note: Check trailer and TV tire pressures when cold; and if pressures exceed the maximum printed on the sidewalls after they heat up, DO NOT LET AIR OUT! Tire manufacturers know that pressure increases as tires heat up, and your tires are designed for this slight increase/overage.

* Wind resistance increases exponentially with speed, and fuel consumption at 75 mph is drastically higher than at 65. If you normally cruise at 65, 55 will also result in significant savings. On the highway, set cruise control to 55 mph maximum (or lower, depending on posted speed limit). The goal is to cruise around 2-3 mph slower than other traffic (except semi's), so that nearly all traffic is going the same speed or faster than you are; and you are NOT passing any other vehicles, except those bogged down on long grades. To maximize fuel economy, do NOT exceed 55 mph.

* Keep your foot off of the accelerator AND the brake, as much as possible. Resist the urge to pass vehicles in front of you, if they are going a reasonable speed. In addition, allow your vehicle to coast when slowing; and minimize brake use. Every time you push on either the accelerator or brake pedal, you are dumping gas and money down the drain. Your cruise control computer is smarter than your right foot when trying to maximize fuel economy.

* If necessary, slow a couple of mph to stay behind traffic, or pass using the accelerator as lightly as possible. If you are passing more than a few vehicles per hour, you are going too fast. The goal is to stay on cruise control as much as possible, and not exceed 55 mph.

I would be surprised it you don't get a couple more mpg out of your existing TV.

Also, despite the few extra dollars spent at the pump when fuel prices go up, that amount is far exceeded by new car payments and higher insurance premiums on a new vehicle. You probably researched your TV thoroughly before buying and justified the purchase in your own mind. Nothing has changed except your perception, which is influenced by a couple of extra dollars spent on each fill-up. If that bothers you, try buying your coffee for the morning commute at McDonalds instead of Starbucks (it's actually pretty good).

Please post your results, as I'd like to see if this helped you as much as it did me.

Good luck!
Hi,
I am pretty close to your recs already. I inflate TV and TT tires to the maximum rated pressure. And I monitor them all with TPMS.

I drive at 55 MPH as my basic speed. Sometimes 58, but never over 60. For one thing, getting a ticket in California will cost about $1,000 when insurance hikes are included, so I have a lot of incentive to hold speed down.

My mileage hangs around 10.6 for trips of a few hundred miles. We once drove 300 miles against a headwind and I got 8 MPG for that segment.

So, with my current TV, I think I am squeezing it as best I can.

My O/P here was a bit more "wishful thinking" than trying to get my current rig up to 15 MPG - an exercise to wonder if there is a better way to look at the towing problem than just getting a big PU/SUV.

I don't know much about diesel - never owned one.

Years ago, people did use big sedans to tow 25 foot trailers. Are there any of today's sedans capable? Would they get better mileage?
__________________
mstephens is offline   Reply With Quote
Old 09-16-2012, 01:14 PM   #14
Rivet Master
 
mstephens's Avatar
 
2013 25' Flying Cloud
Cat City , California
Join Date: Sep 2012
Posts: 854
Quote:
Originally Posted by idroba View Post
I have towed the same 20' '74 Argosy, 4200#, with a Jeep Grand Cherokee straight 6, 190 hp, a Jeep Grand Cherokee V8, 270 hp + or - (can't recall) and now a Jeep Grand Cherokee with the hulking Hemi V8, around 380 hp. Same areas, same trailer, same driver, same patterns of use. In each rig my milage has been, by actual measurement over long time periods, 13.5 mpg.

So, no, it is not the hulking engines that are doing it. Overall mechanical resistance and aerodynamics would be my guess. BTW, the latest Grand Cherokee gained 1000 # over the old ones. Same milage however.
That's an interesting set of observations. I guess the conclusion I would draw from that is efficiency has gone up so much that you get the bonus of 380 HP with no penalty in mileage. Pretty good bargain.
__________________

__________________
mstephens is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 10:06 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.