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Attached you will find my approximate route for the trip we completed this last Monday. Pics of trip computer, scale ticket, and truck/trailer setup also included.
Cruise was set to around 78-80mph most of the time.

Here is my situation and question to anyone who knows.

We travel alot for work and are full time RV'ers. Our travels could well bring us over most of the western 2/3rds of the country eventually. Planing on pulling this 5th wheel quite abit this year. Truck is mechanically stock, pulls great, that stretch of I-10 we did has multiple fairly long grades of 2% and it never even downshifts for 2%, once we hit 3% it does sometimes. Power is not really and issue, sure I'd love more but I could live with this. Fuel mileage is where its getting pretty thirsty I feel. On level road it gets around 7-8mpg at 80mph. At 70mph it gets about 1-1.5mpg better or so.

Would a Derringer help, and if so how much?

Deleting is out of the question right now but I am curious if there are any other reputable tuners out there, including the Banks Derringer, that would help me get better mpg while towing without having to swap ECM's etc.
 

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Thank you for the replies.

I one of those guys I guess.. I would really struggle to get myself down to 65 in a 75 or a 80... May have to consider that though

Anyone know about how the Derringer or tuning options would impact the numbers at 75-80?
 

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Thank you for the replies.

I one of those guys I guess.. I would really struggle to get myself down to 65 in a 75 or a 80... May have to consider that though

Anyone know about how the Derringer or tuning options would impact the numbers at 75-80?
BLUF: I don't own a Derringer. What follows is pure pontification, albeit arguably well-informed pontification.

I don't know about the effect on fuel economy, but I'm extremely skeptical that it would offer improved fuel economy. The goal of those tuners is to increase power, not necessarily fuel economy. Your vehicle's drag coefficient, the speed at which you're traveling, the weight of the rig, and the grade you're ascending determine the power required. Fuel consumption is approximately linear with power, and it's very unlikely that there's any tuning that could allow the engine to produce the same power with less fuel consumption. That would be a thermodynamic miracle, to be honest.

Additionally, if you run the stock configuration, you can be confident that the engine isn't going to turn itself into kibbles and bits even at WOT with a load because the factory tune was set up specifically for that scenario. As soon as you deviate from that configuration all bets are off, and you'll have to be extremely careful about how hard you push the truck with a load, especially in hilly areas. Personally I like being able to set my cruise control when I have a trailer hooked on and let the engine and exhaust brake handle things. With a tune your cruise control may inadvertently run the engine at maximum HP (beyond design HP) for an extended period of time while ascending a hill, which is a recipe for disaster.

This is why the engines in the commercial variants are generally tuned for lower max HP; since they're generally expected to be run at max output continuously (not just for a few seconds under hard acceleration without a load), it's safer to keep the engine at a lower power output. It seems a bit ironic but it makes sense.
 

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Well I don't think your gonna get much better than what you have now. I don't see a programmer/inline tuner really doing much for you as far as towing mpg.

I just went on a 2000 mile trip over Christmas with my fifth wheel (grossing just under 24k) and I averaged right at 9 the whole time. And that's with truck in my signature here.

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I have done 2, 1400 mile round trips at 24k gross towing the camper. Towing at 65 MPH my mileage is a pretty steady 10 MPG, bone stock.
 

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Yeah speed will make the most difference for sure. My trip was all around 75 mph, if I would have been at 65 I'm sure it would have netted a mile or two better.

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Derringer will do nothing but lower MPG's, (or keep the same on stock setting) certainly not improve them..

Why get it? if you feel you want some extra pep when merging / passing, then bump up to lvl 3, and once cruising again, bump back to stock....

"Pedal commander" claims to have an economy mode... I don't know any real life feedback.. and with that trailer, I doubt you want to make the truck anymore sluggish...

Good luck..
 

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Yep, aerodynamic drag is a squared function, double your speed and square the drag.
As a professional nitpicker, I'll point out that if you double the speed you quadruple the drag, not square it.:nerd:

But you're right that the force due to drag scales with the square of velocity. And since power = force * velocity, the power loss due to drag actually scales with the cube of velocity. So going faster is generally much less fuel efficient, assuming no limitations due to hearing.
 

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BLUF: I don't own a Derringer. What follows is pure pontification, albeit arguably well-informed pontification.



I don't know about the effect on fuel economy, but I'm extremely skeptical that it would offer improved fuel economy. The goal of those tuners is to increase power, not necessarily fuel economy. Your vehicle's drag coefficient, the speed at which you're traveling, the weight of the rig, and the grade you're ascending determine the power required. Fuel consumption is approximately linear with power, and it's very unlikely that there's any tuning that could allow the engine to produce the same power with less fuel consumption. That would be a thermodynamic miracle, to be honest.



Additionally, if you run the stock configuration, you can be confident that the engine isn't going to turn itself into kibbles and bits even at WOT with a load because the factory tune was set up specifically for that scenario. As soon as you deviate from that configuration all bets are off, and you'll have to be extremely careful about how hard you push the truck with a load, especially in hilly areas. Personally I like being able to set my cruise control when I have a trailer hooked on and let the engine and exhaust brake handle things. With a tune your cruise control may inadvertently run the engine at maximum HP (beyond design HP) for an extended period of time while ascending a hill, which is a recipe for disaster.



This is why the engines in the commercial variants are generally tuned for lower max HP; since they're generally expected to be run at max output continuously (not just for a few seconds under hard acceleration without a load), it's safer to keep the engine at a lower power output. It seems a bit ironic but it makes sense.


I am going to have to nitpick about the engine running at max HP with a tune. Most tuners do not allow the truck to run at peak power ESPECIALLY in the tow tune or tune 3 whatever you want to call it.


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I have to agree with most of the other comments. You can be in a hurry or get decent fuel mileage. If you feel the need to run 80mph, you'll have to pay for it. Nothing is free.

I pull RV's professionally and what you're pulling (the OP) is right in my wheelhouse. I pull 5ers grossing 24k+ routinely. When you're doing it for a living, maximizing profit is key so cruise is almost always set right about 65mph as most RV haulers do. In fact, I pass more of them than pass me. I get about 10mpg with an LML. Empty, I get 15-16. I'm amused at all the guys getting 21-22. I can do that too......at 50mph. Who does that? But my point is, speed is the #1 determination of fuel mileage.

You just have to find your own personal balance between speed and efficiency.
 

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I am going to have to nitpick about the engine running at max HP with a tune. Most tuners do not allow the truck to run at peak power ESPECIALLY in the tow tune or tune 3 whatever you want to call it.


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But they'll allow the engine to run at power levels beyond the engine's design power, thus jeopardizing the entire power train when the truck is power-limited...which is often the case when ascending a grade with a load.
 

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But they'll allow the engine to run at power levels beyond the engine's design power, thus jeopardizing the entire power train when the truck is power-limited...which is often the case when ascending a grade with a load.


True but power levels beyond design typically will not cause much harm given that the stock tunes are fairly conservative. Yes if you crank it to tune 5 with a 25,000 lb. trailer and do it routinely you’re going to have issues


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We routinely pull our 35’ fifth wheel and usually have the cruise set to 64. We find this is fast enough to pass most of the big rigs but slow enough to stay in the right lane. Last long trip (4500 miles from CA over the Rockies and back) we averaged 10.9 mpg for the trip (hand calcualted). We only had 6 or 7 thousand miles on the truck for that trip. We have just over 20k now and have a similar trip planned for May (about 4200 miles though). We will see if the mileage has improved any with the “break in” done. As others have said, MPG will be greatly effected with increased speed. I can bump the speed up a few MPH and watch the MPG gradually drop.
 

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65 seems to be a sweet spot for me also. Running with the CTS2 on tow mode. +60 hp. 12 mpg on flat. 11 combo thru N Carolina pulling 18,000 5er
 

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I pull the same size rig @ 65 mph & get 11-12 mpg, try slowing down, your tires are not rated for 80 mph you'll have bigger issues than fuel mileage.:laugh:
Being safe is the priority. I started out doing 75 mph but soon found out that my tires are rated for 75 mph. I like to stay under so I slowed down and gained fuel mileage.
 

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Towing that big a trailer at that speed and load reminds me of the Chris rock quote. “ you can drive with your feet but that doesn’t make it a good idea”. Slow it down and you’ll be safer and get the mpg increase.

I do recall seeing a YouTube video of the derringer increasing mpg while towing.

 
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