Normal.

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Respectably.....:smile2: You bought the wrong truck. A trailer of that size/weight, 70-75 tow speeds, a 3.42 gear would have been much better for you. The 4.10 gears at your speeds has the engine spinning pretty fast which hurts your mileage.......slow down and the mileage will go up. For comparison, my 3.42 truck, 10,500 lb fiver @60-65 mph is usually 11 to 12 mpg.

Sam

 

Yeah, the 4.10's were the only thing I wasn't crazy about with my truck but the deal was too good to pass up. I would have liked the "middle ground" 3.73's. Guess I could slow down...

 

There are so many variables to consider when trying to determine "Normal" mpg, towing or empty. Terrain, driving style, weather, trailer aerodynamics, and of course take everyones numbers with a grain of salt, as some will be "inflated" if you will.

For what its worth, I am right around 9mpg towing 28k through the Rockies. Generally in the 60-70mph range.

And when I tow my 28' V Nose enclosed, that weighs half as much, I get the same mileage.

YMMV. :grin2:

 

I'm with Sam, slow your speed down your turning 2100-2200 RPMs at those speeds plus dragging a trailer behind you. I pulled this 40' GN trailer from NC-GA in may of this year weight was probably 9-10k never went of 65 unless I was passing someone my mpg was 10-12 and not even 2k miles on the truck.



Pulling this with my 2500 weight was probably identical to the other one, I didn't go past 4th gear due to trans issues so RPMs were about the same as my dually and mileage was also about the same.
.

 

Cool!! Yours is the first llcb Black appearance package I've seen besides mine.

 

I have been getting 11.2 average towing a 8000 pound 35' travel trailer at 70MPH prior to getting a new 43' 5'er toy hauler at 16K that now gets 9-10MPG at 65-70. I have a G56 manual tranny with 3.42's. So I'd say yours is normal for what it is. Slow down. It will get better. Those ST tires aren't meant to go that fast anyway.

 

Michelin Pilot Sport PS2 225/40R19 93Y XL with rim protection ridge (FSL) - giga-tires.com



Trailers are so different. Wind resistance, as well as weight.

And Arizona is not NC.

Over the years, I have noticed a difference in towing when going home on a round trip. Wind? Temp? I have no idea.

So no one can tell you whether your truck is doing as well as theirs or worse unless they followed you.


So unless we both filled up at the same pump and inflated our tires to exactly the same, made sure our truck and trailers weighed exactly the same and then followed each other, we would never know.

I pulled my 4 horse trailer, the long centger loading model, over a hilly route in SE VA and it hand calculated to 13.04.

Drove exactly the same route one week later and the miliage was one mile per gallon less.

The first trip was on a beautiful night going East and ordinary weather going back West.

The second trip was a terrible foggy rainy night going East and rain going back West.

Was that a reason for the lower MPG? I have no idea.

But aviators know very well the effects of temperature as well as high moisture in the form of rain or even high humidity have on aircraft engines.

So my advice is don't seat it, don't fret it.

Take a few months and check it again.

 

I think 8-9mpg is normal towing a large profile (non flatbed) trailer like a camper or toy hauler at highway speeds.

My 15 Ram 3.42 Aisin, '13 Ram 3.42 68rfe, Ford 6.4 and GM LLY Duramax all got 8-9mpg towing different 8-10k lb campers over the years.

 

I agree with others that if you slow down you'll get better mileage, not to mention the fact that unless you've changed tires on your RV they are probably only rated at 65mph. As far as the 4.10s, towing I bet you wouldn't see more than 1mpg difference if even that much with the higher 3.42 ratio. The new trucks with the Aisin trannys and possibly with the 68RFE I believe are geared nearly the same in high gear to compensate for whatever gear ratio you have in your axles. I have 4.10s in my 2015 4x4 crew cab dually and get 9.8-10.5 towing my 30ft toy hauler loaded to about 12K at 65mph. If I go slower at about 55mph, mpg goes up to about 11.5. Empty it will easily get 19-20 at 65mph and jump to 22-24, calm day, level road at 55mph. I doubt the gear ratio is hurting you nearly as much as your speed.

 

Those of you familiar with NC will know I-77 between the VA line and Charlotte.

The grade at Fancy Gap to the NC line is pretty steep.

One day I decided to not touch the brakes on the way down. I was driving a F350 1999 manual. Pulling a 4 horse trailer loaded the same as one horse.

The truck stopped gaining speed at 70 MPH. Maintained that all the way down. The drag chute effect.

Have not been that way in several years now, so I have no idea what the present combination would do. It is much heavier and might be slightly more streamlined.

But drag is a big deal.

 

As others have stated, it's all aerodynamics. The flat plate area of the front of your camper is like a billboard. Aero drag increases exponentially with speed. I wouldn't be surprised if it doubles from 55 to 70mph.

 

My thoughts exactly. The drag at 70 is greatly enhanced when compared to the drag at 65. It doesn't seem like 5mph would make that much of a difference...., but it does... and especially if your burning up the hills at 70-75 mph.

 

Sounds about normal to me for the speed you are going. I have a second gen 24v 4 wheel drive auto/3.52 rear end, stock tire size, free flowing exhaust and 275 hp injectors and at 65-68 mph I get 10.2 to 12 mpg. That's with 60K plus towing miles pulling a 10000 lb fifth wheel. Over the years I have tried many different speed and driving scenarios without much change, not more than .5-1 mpg difference in mpg. Tried the 55 mph deal many times (what a pain the ) still not much of a change. Perhaps .5 to .75 mpg increase BUT more wear and tear on the transmission due to constant or frequent down shifting at every slight grade (RPM just to low). For me at 62-68 mph is a sweet spot running around 1800-2000 RPM +-.
Congratulations on the trailer ! Watch your trailer tires at the speeds you are going. .

 

I average 9 10 mpg pulling 24000 lbs with my sig truck.

 

I did get 11-12 with this camper

 

Towing a 10k# fiver going 60-65 I'm averaging 11-12. As soon as i punch it up to 70 or faster the MPG's plummit to the 8-9 mark.


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Just finished a 5,000 mile round-trip from AZ to FL pulling a 12.7k 5th wheel (CAT scaled) with the cruise control set to 63 MPH. Averaged 10.6 MPG for the entire trip. Everything hand calculated. No significant wind during the entire trip.

Hand calculations were always about .6 - .8 MPG lower than the EVIC.

Worst mileage was 9.3 MPG driving through the Texas hill country on I10. Best was 11.8 MPG driving thru the coastal flats in MS, LA, and south FL on I10 and I75.

 

Weight doesn't play nearly as big a factor as wind drag does.

With my truck, I average 9 mpg pulling a 40' toy hauler with a less than ideal front cap. I pull this trailer at 65-68 mph.

Same trailer pulled by my previous truck with 3.73's averaged me 8 mpg at the same speeds.

With the 4.10's vs. the 3.73's, I'm penalized about .5 mpg when empty but make most of that up with better mpg while towing.

 

1. Your trailer's listed GVWR is 10k lbs. That's likely what it weighs with all your gear in it.
A trailers "dry weight" rating should always be ignored.

2. As was mentioned, your trailer likely has crap Chinese ST trailer tires on it.
Towing at 70-75mph is absolutely dangerous with a bumper pull trailer and with those tires.


3. Towing a 10k trailer at 70-75mph and then talking about mpg is ridiculous.


You are new to towing and you are making many mistakes...

 

I have 4.10 gears in my truck (with 37" tires). Towing an extended height enclosed trailer at 75 to 80 mph I get 8 to 9 mpg. Towing the same trailer over the same route at 65 mph I get 11 mpg. With stock tires 4.10 gears will put your engine RPM in the sweet spot at 60 to 65 mph. 3.73 gears will put your engine RPM in the sweet spot at 65 to 70 mph. 3.42 gears will put your engine RPM in the sweet spot at 70 to 75 mph. When choosing gearing choose the ratio that will put your engine RPM in the sweet spot at the speed you intend to tow at. You don't need lower gearing to improve power with these 900 ft lb trucks.

 

I was getting ~9MPG in my 5.7 HEMI 2500 pulling my trailer. I truly thought I would get ~12 or better with a 6.7. But to my dismay, I'm seeing ~9 to 10MPG..?

Basically my 5.7 HEMI and this 6.7 pull about the same. Only major thing I've noticed is improved hill climbing. 6.7 will pull 65 to 70 no matter the hill. The HEMI would slow to ~45 or so. But on flat road, I'd say about the same.

 

If your RV has C rated tires, the max speed is 65 mph. You are pulling a parachute down the highway. Slow down and your MPG will increase exponentially regardless of axle ratio.

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I am currently pulling a trailer very similar to yours, a 34 foot 8200 pound travel trailer. I came from Helena Montana on my way to Boise. Driving through the Rockies crossing the continental divide four times at an elevation of nearly 5000 to 7000 feet variance
I filled up in Dubois Idaho. And I got 8.2 miles to the gallon at that point.

From that point I am coming through Pocatello Idaho. At 75 miles an hour again still, and now I'm getting 10 miles to the gallon. The elevation is about 4500 feet. However the terrain is immensely flattened out.

My question is this, with a 3.42 gear ratio, what is the sweet spot for the RPM range. I have it on tow haul and I watch my gears on my cluster. I like it when I lock out sixth and make it only in fifth gear. At about 21 to 2200 RPMs however if I do not lock out six gear I drop down to about 1600 to 1800 rpm's
Coming from my second generation Cummins, I'm assuming the sweet spot is still right around the 2200 to 2100 range? However I have yet to see much of a fuel mileage difference between fifth and six gears


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So from Dubois Idaho to Mountain Home Idaho I did 70 - 75 MPH and locked out of 6th the whole time, and got 10.5 MPG. No curse control, and when I went down hill i up-shifted to 6th then back to 5th. kept the RPMS up to 2000+. Alt. was 5500' - 2,500+'
Tire PSI was 55-57 psi all around.

That was MUCH more acceptable at 10.5 mpg.

I'll update my same set up going from Boise to Salt Lake City this weekend, but I'm going to bump up my tire PSI To about 70 front and 75 rear. On my Stock Firestone's.

I had to go about 65 at the very slowest in 5th to keep the RPM's in the right place, north of 2K. At 70 I was a needle above 2K in 5th. And yes, my trailer tires are rated for 75 mph. I like the 70 mph mark so far, but trying to get home to mom and the kids its a big + and 75 is even better.