15 MPG Pulling a FC 25!

[mstephens]

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)

[SteveH]

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)

[mstephens]

Originally Posted by SteveH

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.

[SteveH]

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.

[ElCamino Man]

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

[Tim A.]

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

[Bill M.]

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.

[dkottum]

15 mpg diesel is not equal to 15 mpg gas. Costs more, not to mention purchase, servicing, repair prices.

doug k

[Bill M.]

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.

[Phoenix]

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!

[Denis4x4]

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!

[idroba]

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.

[mstephens]

Originally Posted by Phoenix

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]

Originally Posted by idroba

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]

Originally Posted by Bill M.

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.

What sort of vehicle exactly are you using with a little 6 cyl?

[xrvr]

That would be a dodge truck. I get 15 to 16 towing with my cummins at 60 mph. Jim

[Phoenix]

I should allow Bill M to respond, but the Cummins 6-cylinder is a diesel, most likely in a Dodge pickup. Excellent engine; wish they would put one in a Tundra.

We had an old, 1978 Chevy crewcab pickup with a 454 V8. It would tow anything, but it sucked gas! Our average fuel economy towing our Bambi was 7-8 mpg, and about 3-5 on long hills. Our absolute worst gas mileage was on an uphill stretch approaching Flagstaff with our Bayliner in tow (cabin cruiser on a triple axle trailer); 2.5 mpg -- Yikes! We watched the gas needle drop a half-tank (on one of two 16-gallon saddle tanks) over a 5-6 mile stretch. So your 10.5 doesn't sound too bad.

I guess I should have asked details on your Suburban. What year and engine do you have? -- If your Suburban is an older model, a newer one would probably get better fuel economy.

Our current TV is a 2008 Tundra CrewMax, 2WD, with 5.7L V8; and we get about 13.5 mpg towing, on average. Our best towing mileage has been 16.5 mpg in the Rockies where speed limits were 35-45 mph; and the grades didn't seem to negatively affect mpg's. Our worst was 11-12 mpg while cruising on interstates at 75 mph; and we don't do that anymore (one quick trip to a funeral after switching to 16-inch wheels and LT tires).

The purchase of the Tundra was justified because of "Hal's" (the Chevy crew cab) age. Beside sucking gas, Hal was turning into a money pit that broke down almost every time we took our Bambi out.

Note: The Chevy earned the nickname Hal, from the computer in the movie "2001". Every time we talked about buying a new pickup, Hal would break down on the road. We knew he could read lips; so we started closing the curtains and whispering whenever we were at the dining table in the Bambi, and the discussion turned to new pickups.

[slowmover]

Plenty of threads on this very subject, just as with causes of sway or WDH brand particulars. A search will be revealing. I recommend the revival of an older thread that looks promising to you (the OP).

As far as TV fuel economy goes, first, it is the relation of miles towing versus miles solo. Obviously the equation tilts towards best solo mpg that can also tow the trailer. Leaves out trucks entirely no matter the size of A/S.

Second, fuel consumption is only an indicator, a subset of concerns under a larger umbrella of Economy. The big one is the initial purchase price of both vehicles against depreciation (or repairs/restoration) understood as nights of use. All other questions about "economy" flow from that. It is the place to start (as only an individual can answer this per his private business).

More detail about general problems/specifics of FE in RV'ng in a post from, "Aerodynamics of It All" - iRV2 Forums as comparisons in the RV world are fraught with unaddressed problems.

.

[perryg114]

Is the burb paid for? You can buy a lot of gas for $40k+ for a new tow vehicle. Everytime I think of even buying a used car that get 35MPG versus the 20 MPG my Ranger gets I start thinking of the break even time. Even for a cheap used car, it is several years down the road before break even. Now if someone gave me a higher MPG vehicle the choice would be easier.

Perry

[Wayward]

If gas prices are moving you to a new tow vehicle that gets better mileage, buy it soon! The same thing that has driven up the gas prices (money printing) is going to add $3-5K to a decent sized truck over the few years (inflation due to devalued dollar).

Replacing the crime syndicate running the Treasury and the Fed will do more to return the freedom of the road, than replacing our TVs.

IOW... treat the cause rather than the symptom.