Trailer Weight Vs. Fuel Economy

[nhtope]

Hello,
I have been going back and forth on how to improve my fuel economy. Our current set up is a 2013 Chevy 4X4 2500 hd with 3.73 gears gas. I know that diesel would have been the way to go but it was too expensive. We pull a Wilderness 3150ds. It is 6700lbs dry so I am estimating it at around 8,000 loaded. We also tow with a Hensley arrow. Currently I am able to get about 7 mpg. We would like to venture further out west but I am concerned with how often we would have to stop. Would going to a lighter trailer that is a little shorter help with this? For example I have seen some 26 foot trailers around 5,000 lbs. Would it be enough of an improvement to be worth a trade in? Any advice would be greatly appreciated. one last thing. Do the vehicle tuners like the Bully Dog help with this at all? Thanks

[Turbo_Diesel_Du]

We have a 2012 2599 4X4 6.7 Ram and we got 7mpg at times towing our 34ft TT this past June with a huge side wind!! Started at 13mpgh and as our direction changed West to NW milage plummeted. Just kept on going until we got flooded out in Canada and turned back.

[qtla9111]

Like everyone says, wind resistence is the enemy. No matter what setup you have; fifth wheel, TT, motorhome, the results will be the same. All of the combinations I have had of different SUVs and TTs the best is 10 mpg at 55 to 60 mph.

The exceptions are PUPs and folding trailers such as Aliner, Chalet and Trailmanor. I've had two Trailmanors and the mileage improved to 16/17 mph proving the issue is wind resistence. Class B van motorhomes also do well because of the aerodynamics.

[APT]

How fast do you drive? I tend to use about 10% less fuel at 60mph than 67mph.

4000 pounds or 10000 pound RV, they all get about the same fuel economy on the highway.

[popoagie]

the comment on lower profile is a good one.... had same weight and size V nose 16'dbl 3500 axle work trailers... one was 7'+, other is shorter... just 6' + a little... made a 25% difference pulling mileage measured over 5000 miles...cummins diesel pulling it... wind resistance is important

[rfryer]

I’m afraid there’s little you can do, air resistance is the main culprit. The best you can do is keep the speed down as suggested. The weight will become most noticeable when you come west and get into the mountains. Then the TV will really be working to pull that weight up the grades.

You’d have to go a LOT shorter and lighter to see any significant improvement in mileage. I get 14 overall with an F150 4x4 5.4 and 3:55 axle. It hard to track mileage towing in the mountains, but I know my worst case was 9. Generally I do a little better than that. But I’m pulling a 16’ 3000# loaded TT. I don’t really know, but my guess is if I were pulling 5000-6000# I’d be a lot closer to 10 than 14. If you’re pulling that big a TT it’s pretty evident that radical a change won’t happen, likewise neither will the improvement in mileage.

Gas prices can be a pain for me, too. But if I want to travel I have to grin and bear it. I try to cut other expenses to subsidize it. I prefer national forest or similar camping so my camp fees are far less than if I used commercial parks. And we don’t eat out a lot, another potentially expensive addition to the trip. So I muddle through that way.

[Longtrace]

Presuming an engine is equally efficient at all speeds (which is very incorrect, but makes it almost possible to figure out a solution), then "fuel use" = "power required". And if the rig is not accelerating, then "power required" = "total resistance to moving". This "total resistance to moving" is composed of "air resistance", "rolling resistance" and "mechanical inefficiencies".

Of these, weight really only effects rolling resistance. Technically, on a one-way trip, the down-hill journey will require less fuel - but for any round-trip, the amount uphill is compensated for the downhill part.

Rolling resistance is the major component of "total resistance to moving" only at low speeds. Like less than 30 mph (48 km/hr). Once speeds get above that, air resistance very quickly becomes the dominant component. The air resistance is related to the air speed squared. So all else equal, changing the weight will have almost zero effect on fuel use at highway speeds.

The other situation where weight is a factor is acceleration. The more times you have to speed up, the more fuel you will use. Minimum fuel usage when accelerating will be when the engine is operating in it's peak efficiency RPM range. That varies depending on the engine. The suggestion to monitor fuel use with a ScanGauge or the like (if your vehicle can connect to one) is possibly the easiest way to figure out where your engine is most efficient. But that will not help when cruising on the highway, only when speeding up. (stop sign, stop light, on-ramp, etc)

[mooky_stinks]

nhtope wrote:
Hello,
I have been going back and forth on how to improve my fuel economy. Our current set up is a 2013 Chevy 4X4 2500 hd with 3.73 gears gas. I know that diesel would have been the way to go but it was too expensive. We pull a Wilderness 3150ds. It is 6700lbs dry so I am estimating it at around 8,000 loaded. We also tow with a Hensley arrow. Currently I am able to get about 7 mpg. We would like to venture further out west but I am concerned with how often we would have to stop. Would going to a lighter trailer that is a little shorter help with this? For example I have seen some 26 foot trailers around 5,000 lbs. Would it be enough of an improvement to be worth a trade in? Any advice would be greatly appreciated. one last thing. Do the vehicle tuners like the Bully Dog help with this at all? Thanks

You need to let us know your driving habits. What speed do you cruise at? I have the same truck and a simular TT (8500#) and I have been getting 8-9mpg. I tow at 62-65mph. I'm not sure how the terrain is where you tow as that can have a big effect on mpg. I can go about 300 miles on the 36gal tank. I can't imagine wanting to drive longer than that without stopping.

[Slowmover]

Operational cost -- FE in this instance -- is mainly a question of vehicle specification, both TT and TV, first, and second, age/miles of vehicles in consideration. One starts from scratch to get the best from both. This is the way I put my combined rig together. My folks saw 7-8 mpg with their mid 70's Cadillac pulling a TT just like mine, only shorter. I bought a TD DODGE truck and see 15 mpg overall with a 35' TT with a 9k GVWR. I spec'd truck for best mpg and longest life at lowest cost (2WD, manual trans) and bought used. Same for TT: best condition at a price I could afford (trailer brand is an upmarket cousin to Airstream; in sig). Long life at lowest operational cost, not just a low purchase price, was key.

Now, both need money into them (age/miles), but the experience is consistent with more than a dozen others using pre-2008 Cummins powered Dodge trucks pulling 28-34', 8k-11k aero aluminum TT's.

To get the best of them is to follow the usual FE guidelines: low travel speed, zero idling, best book maintenance. To that I would add best hitch rigging, brake controller, etc. Mechanical baseline on both vehicles is vital as FE is a matter of details adding up: bearing adjustment, brake adjustment, alignment on both, no steering slop on TV, etc.

SMART SPEC is followed by SMART USE. Where can you decrease the non-towing miles the rest of the year? Do a better job of combining trips and avoiding cold starts, hard acceleration, idling, etc, and the savings under a fixed annual fuel budget can make a serious contribution to your vacation budget.

Closed shoulder highway rib tires are best for mpg. Worth more than 1-mpg. See the BRIDGESTONE m500 and maybe the r700 models. Stay with stock sizes.

Look to TRANSFER FLOW, TITAN and others for increased fuel range tanks. A 65/gl tank (if available) would give one a 500-mile range at 8-mpg. Really, if one is only traveling 300-miles/day, then less would suffice (as gas engines are more affected by increased TV weight).

I also recommend a SCANGAUGE or ULTRAGAUGE to give driver feedback. 60-mph at the highest vacuum reading is ideal. Also, it is important, IMO, to plan stops in advance. Fuel, food and rest breaks. Keeps the driver alert to the problems of the moment.

And, setting up your hitch rigging on a certified scale (and getting best TV tire pressures thereby) is highly recommended for keeping rig wander to a minimum. As before, all the little things add up. While hitch rigging isn't "little" it does have an effect on FE even if slight.

Most of all, remember that it is the percentage increase to the baseline MPG that counts:

From 7.5 mpg to 9 mpg is a 20% decrease in fuel burn!!



Good luck

.

[GaryUT]

Wind resistance and how you drive make the most difference with mpg.

If im in a hurry to make a destination I travel 65 mph, and I get 7-8 mpg.

If I take my time and do 50-55 mph, I get 9-10 mpg.

I try to plan trips so that I dont have to travel more than 300 miles in one day. We usually stop every 150 miles or so, I dont like to let the fuel get below 1/4 tank, and someone usually needs a restroom break anyway.

Gary

[skipnchar]

Changing tow vehicle will make more difference than changing trailers. You can maximize your mileage by changing driving habits but will always be limited by what the truck can do.

[naturist]

I'll agree with the others that how you drive and wind resistance are both much more important than weight. I had occasion to drag a car on a dolly 200 miles and back a couple years ago. Weighed almost as much as my TT. I got 18 mpg towing the car/dolly, and I get 14 towing the full height/width TT. Beyond that, I towed that TT into a 50 mph head wind on two separate occasions, and got 9 mpg once and 10 mpg the other time.

If you are wanting to improve mileage badly enough to replace your TT, I'd suggest you look into something like a Trail Manor that has a lower profile while towing before you consider a lighter rig.

[Bob_Olallawa]

romore wrote:
You likely won't see a big improvement, certainly not enough to down size the trailer. I find my right foot has more to do with mileage than anything, 55-60 seems to be a good speed. Any more than that I pay.

What he said, been there done that and had the small tank with the short bed. Upgraded to diesel when it was time to trade trucks. Never catch up money wise but sure is nice not having to fill up in every town.

[Desert_Captain]

I would recommend a wind deflector, particularly if you have a shell and can mount it back close to the front of the trailer except that I don't have the inclination or energy to argue about how well they can work. For the record we consistently got an additional 1.5 to 2.0 additional mpg towing a 5000# TT with my F-150 SCab. PM me if you would like details.

What will work without much argument is to simply add a Scan Gauge and then pay attention to what it is trying to teach you about fuel economy. Most folks find an additional 8 to 10% improvement but this will involve backing off that right foot which some folks are loathe to do. Bottom line it is always going to be an 8000# brick and the wind is not your friend. :S

[downtheroad]

Gdetrailer wrote:
You are not going to gain much if any by downsizing.

I have said before, if you are worried about mileage, sell the RV, buy a Prius and visit Hotels and Motels...

Right on the money..
and you will never make up the difference by taking the depreciation hit selling your current rig.
Also you will likely be giving up some comfort...loose, loose.

Forget about mileage. Once you do, you will enjoy camping a lot more