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Old 11-21-2017, 09:04 PM   #1
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Fuel Economy While Towing

I've found something interesting... wondering if anyone else has noticed something similar.

I have a 2013 Silverado 3500 diesel. It's got a flatbed and a ranch hand front bumper, so fuel economy isn't quite what it could be. I deleted the EGR, DPF, and DEF systems, which gained me quite a bit of mileage. I get right at 20 unloaded cruising along at 70. It drops down to about 17 once I get to 80. Pulling my fifth wheel, which is 42-43' long and weighs about 13,500 loaded down with everything, with about 2350 on the pin. I average about 12.5 mpg towing it at 65mph. I am pretty happy with that. I'd love to see 20+, but being realistic, I think that's pretty good. Those are hand calculated numbers, not DIC.

Now, I also have a Polaris Ranger Crew, which weighs about 2000 lbs. I pull it on a 16' Gatormade utility trailer, which weighs about 650lbs I think. I get about 10 mpg pulling it. Same speeds, same roads... Makes no sense to me. The camper is almost 6 times as heavy, almost 4 times as long, and sticks up above the cab significantly. Wind resistance alone doesn't make sense. I can't even begin to figure out why this is the case. We'll see this summer what happens when I pull the Ranger behind the camper. Has anyone else noticed something similar to this with their trucks?
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Old 11-21-2017, 09:12 PM   #2
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Lots of drag on the Polaris compared to the 5th wheel. The Polaris has lots of open spaces that catch the wind. Throw a tarp over it that might "streamline" it some.
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Old 11-21-2017, 09:13 PM   #3
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Maybe get a new calculation over a longer distance. Something not right.
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Old 11-22-2017, 01:12 AM   #4
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Fuel Economy While Towing

I'd say you're way low on your pin weight guess. That's not even 20% but it should be more like 2700#!
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Old 11-22-2017, 10:16 AM   #5
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I'd say you're way low on your pin weight guess. That's not even 20% but it should be more like 2700#!
He's at about 17.5%. All MFG recommend 15-25%. He's within those.
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Old 11-22-2017, 10:37 AM   #6
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I occasionally tow a small open trailer to haul llamas in. Loaded with two llamas it cant weigh more than 1500lbs max. But it does have 2x4 framed railing about 4.5 feet tall so the llamas cant jump out I get 14ish mpg with that trailer and on our fifth wheel it is about 12. If I put 2k of weight in the bed I barely notice the drop in mpg maybe .5 to 1mpg loss get around 18-18.5mpg same drive unloaded I get 19-19.5 so it may very well have to do with wind resistance. this is on a 17 Ram 3500 SRW 6.7 diesel.
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Old 11-22-2017, 11:49 AM   #7
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Fuel Economy While Towing

Your FE comparison needs some rigor. The difference from solo to towing a TT where all else is the same is an average of 40% as penalty since the 1960s.



Truck must weigh the same (without hitch up), the speed must be the same, and it's best to use cruise control AND start-stop from the same fuel pump having run 100-miles or more the same day, or in exact same weather and traffic.



The value of this for everyone is to get a baseline reference (after sorting hitch using scale weight). This reference will be useful in diagnosing future problems against known numbers.



Does your Polaris trailer have a single expanded-metal ramp that is tall when ready for travel? Wind resistance is such that it's "solid".



And, does your TV have mirrors that you move outwards for vision?



Do the test as suggested. 100-mile loop back to same pump. Fill only to first shut-off. Same speed. Use cruise control. Mark down all lane changes, accelerations and braking events not part of entering or exiting road.



All vehicles need to have CONFIRMED proper alignment, brake drag, bearing preset. Filters and fluids changed per schedule.



As a general note, FE is always best below 60-mph. That number is like hitting a wall. With my one-ton hauling my 35' TT I average 15-mpg at 58/9-mph. And have hit 17-mpg. But this is all in the South Central US in mild weather. By itself the truck doesn't ever fall below 24-mpg empty or loaded, day or night, rain or sunshine. Have seen 27-mpg quite a few times. At that speed .

I can pull the 6x6x12 UHaul enclosed trailer at 18-loaded, and 19-empty. (About a 4K lb difference).




Aero matters most for the absolute number. Believe me that we can build s 4000-lb trailer that no pickup of any description can pull at highway speed.

Change but one parameter and the comparisons are without meaning.



.The test must have but one change to be worthwhile.
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Old 11-22-2017, 12:19 PM   #8
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I don't know much about diesel trucks and I'd be curious how deleting the DEF system would increase fuel mileage.
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Old 11-22-2017, 04:24 PM   #9
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I do know wind direction makes a huge difference. About 1.5mpg dif from head wind to tail wind. Towing or not towing.
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Old 11-22-2017, 04:29 PM   #10
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Since DEF is injected into the exhaust, how could deleting the DEF effect fuel mileage? You must have added a TurboAnnihilator from JC Whitney.........
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Old 11-24-2017, 04:00 PM   #11
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What kind of 5 th wheel do you have that is 42-43 feet long and weighs 13.5 k loaded? Do you fill your tires with helium?
I have always found that my mileage goes down when I tow. If you tow primarily in the mountains your mileage will be even lower.
I always like to calculate my mileage on the trip down the grapevine, it usually impresses my younger brother.
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Old 11-29-2017, 09:24 PM   #12
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Lots of drag on the Polaris compared to the 5th wheel. The Polaris has lots of open spaces that catch the wind. Throw a tarp over it that might "streamline" it some.
I agree with MR-D. The Polaris would probably have better aerodynamics if you left it in the original shipping crate. Try towing it in an enclosed cargo trailer and your mileage will go up. Your trailer brakes might be dragging but I think you would notice the heat build up.
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Old 11-30-2017, 10:16 AM   #13
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What kind of 5 th wheel do you have that is 42-43 feet long and weighs 13.5 k loaded? Do you fill your tires with helium?

Where you been man? Been filling the truck and trailer tires with helium for years. Easily makes me a lot lighter. Recently I replaced the air in my air bags on the truck with helium. Bad idea. Back end of the truck wouldn't stay on the ground.

I think the OP must have opted for the optional helium bags that now come on 5th wheels. That is how his 42-43 foot 5th wheel only weighs 13,500 pounds loaded. Gotta keep up with the times man.
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Old 12-01-2017, 08:11 AM   #14
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Since DEF is injected into the exhaust, how could deleting the DEF effect fuel mileage? You must have added a TurboAnnihilator from JC Whitney.........
Deleting the DEF doesn't... but the EGR and DPF, did. Once you get rid of the DPF, the DEF tank is just added weight. The DPF was nearly clogged and was going to have to be replaced. It was a no brainer to delete rather than replace it.

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What kind of 5 th wheel do you have that is 42-43 feet long and weighs 13.5 k loaded? Do you fill your tires with helium?
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I think the OP must have opted for the optional helium bags that now come on 5th wheels. That is how his 42-43 foot 5th wheel only weighs 13,500 pounds loaded. Gotta keep up with the times man.
Sorry guys, it's obvious that the scales that I used, as well as the ones the Manufacturer used, were incorrect. I don't know how I could be so silly. I mean, why would the manufacturer put a sticker on the camper saying it weighed 11,200 or so dry?


Seriously though, the fact that you think it should weigh more even further solidifies the fact that it's odd to get better fuel economy with the fifth wheel. I guess it has to be all about aerodynamics, as someone else suggested.
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