A good friend of mine just got back from a 3,000 mile plus towing trip from Minnesota to Florida and back. He pulled a Flagstaff 8529 5er. 65 mph down and 70 mph back. 10.4 MPG. I thought that was rather low?

 

I think it's pretty close. My fiver is in the 12-13k range loaded and that is about what I get. Bear in mind I don't slow down going up hills, I let it eat.

 

I'm usually pretty happy to see double digit towing MPG, but with the cruise control set at 75-80 pulling a parachute.

 

DRW with 4.10 rear end.

Pulling an empty 32' tandem dual gooseneck at 72mph I get about 11.


With no trailer and running 78mph I get about 13.

With no trailer and running 55mph I get about 20.

 

geesh I am getting 12 around town unloaded. its at like 400 miles I can't imagine it loosening helping a whole lot.

 

Wow, I thought those diesels would be getting much higher numbers towing. Makes me think my gasser isn't doing too bad. Didn't buy a diesel because I only tow about 10% of the time.

 

I get about 11-12 pulling a much more aerodynamic and lighter horse trailer at those speeds with a SRW 3.55 gear.

I wouldn't be unhappy averaging 10.4 with a much taller and heavier trailer.

 

I get about 11.5 towing my fifth wheel (about 12,000 pounds). I usually set the cruise at 65mph.

 

I hauled horses from Northern Utah to Southern Utah for President Day weekend. My GN 4H trailer is about 13,000lbs. My truck has the 3.55 rear end and I had the 295/65R20 tires, So 35" tall.

I got 11 mpg for that 850 mile round trip

I get 17.x on my daily commute empty.

I would guess your buddy's RV trailer has a larger and flatter front than my Horse trailer. So 10.4 mpg seems in line

 

Odd thing is, that most gassers get about 12 unloaded so your towing is much lower than the 6.7L. Load is a factor as is weight, and frontal area. If you tow a small trailer with no or little frontal area, mileage isn't hit that hard. Tow fifth wheel or heavy, everyone takes a hit.
Better mileage with the diesel either way and twice the torque.
Win Win the way I see it.
I'd take the mileage of a gasser to have this much tq (2018 6.7L has 935TQ, 2018 6.2 has 430TQ) or more than twice the TQ. But I'll take way more MPG, My last hand calculated MPG trip was 367 miles, 18.6 MPG. Not using the trucks computer, they are never really accurate in any vehicle I have owned except BWM. Do the math yourself and you will see what your true MPG is, not what the lie-o-meter says. This was hand calculated, only 3k miles on the truck.

This is something I have never understood, people complaining about diesel MPG, better than gas no question, tons more torque, no question. So what is your complaint?

YMWV

 

 

I also tow at 75-80 mph with my 6.7, because it can and honestly at the slightly higher RPM the truck just chugs along up just about any hill in 6th gear with ease. The hit to MPG isn't really a big deal.

 

Don't forget that most trailer tires are rated for 65 mph. You get away with higher speeds in colder temps and shorter runs, but long days in temps above 90 can lead to lots of fun on the side of the road.

Be it gas or diesel, speed kills mpg due to wind and frontal area much more than weight. Does up front cost of a diesel payback in mpg? Probably not even if you haul your load for 100k out of 150k miles. However, if you value how you feel after a 6 hour day behind the wheel hauling a heavy load, regardless of terrain -- you bet. At trade in time, a diesel may give you some more back as a % of extra initial cost, but do not bet too much on that.

 

I used to think that all trailer tires (ST) were rated at 65 mpg. I blew a trailer tire two years ago and pulled in and had a conversation with the tire manager and found he had a lot of choices that were rated up to 80 mph in ST tires.

A lot of our speed limits on the Interstate are 80 mph. Which is faster than I want to tow. But having a tire rated at 80 mph lets me tow at 70 mph with no problems.

A nice thing about the torque of a diesel. is that weight doesn't mean much to it. Wind resistance does. I've towed loaded trailers at 16,000 lbs and then towed empty trailers at 6,000 lbs. Same frontal area, but 10,000 lbs difference in weight and only seen 1/2 mpg difference in fuel economy.

Like I said above, I'm getting 17.x on my daily commute. I'm pretty sure if I took a 400 mile trip empty, that 17.x would jump to 18.x or mayb 19.x mpg. I hauled an elk head ( not much weight) from SLC to Idaho Falls for a neighbor in my 2015 truck and got 19 mpg, Which was better than his Honda Ridgeline running on gas got.

If I rarely towed, the 6.2 Gas is a more cost effective engine. But 1/3rd to 1/2 of my total miles is with some sort of a trailer hooked up. And a diesel make better fuel economy

 

I have averaged about 8 mpg after about 3500 miles towing my 11 k toy hauler with my 6.7 so most of you should be happy. I do have a level kit, 34.8 inch tires and the toy hauler is a tall bumper pull. Plus I drive in the mountains. Sometimes in a headwind I’ll only get about 7.5!