Towing mileage on new 6.7

[Hounddog]

As a first time diesel owner, I based my knowledge on a close friends 5. 9 automatic. He gets 15. 9 mpg towing his 35ft 5er. My new 6. 7 (only 1500 mi) only gets, 10mpg towing my 30' trailer (7000lbs). I know the mileage improves as they get broken in but I'm just curious what others are getting in their new 6. 7. I'm also suspect of what kind of power/torque they're making after these reflashes that are necessary to clear the CEL codes that have plagued new owners. ( I tried to find a new 5. 9 but none were available so I didn't think it would be a bad thing to trust the Cummins name and by a new 6. 7) Thanks.

 

[TAbbott]

I'd have to think that your friend is reading his mpg off his overhead and not calculating it fill-up to fill-up. 15. 9 would be awfully, awfully good pulling a 35 footer unless he's always on flat ground on cruise at 55 or less -- no stops, no wind, no 4x4 or anything. I have a friend with a 98. 5 24 valve 4x4 w/ 5 speed manual transmission that gets pretty phenomenal mileage -- 22 plus running empty -- and he can't get 15. 9 pulling his Montana 28 foot tandem axle.

 

[DonTX]

I can make 14 most of the time, driving 60-65 with my 35 1'2 foot (gross out at 20k). I think your new one will do better as it gets sorted out.

 

[klenger]

I get about 11 towing, FWIW.

 

[DWeiler]

With my 01,stuff in my sig pulling the 11k Titanium 36ft fiver(gross20,000),some good hills but mostly flat pulling at 60-65MPH i managed to get 12. 8 hand calculated. I had to drop a gear a couple of times and scream up at 2500RPM to keep the EGT in check but i maintained/or near the speed limit for the most part. PS I don't think the newer 6. 7 with all the emissions will get much better than the older genner trucks.

 

[JCasper]

I got 10. 7 on my 2,400 mile trip to Yellowstone this last summer with my 26' Springdale that weighs 8,000lbs.



I was driving at 70 on most freeways and ran the Smarty on level 1.

 

[McCRam]

I can get about 12mpg pulling the 33 ft fifth wheel. Don't forget that a new diesel will take thousands of miles to break in. I wouldn't worry too much about mileage until after 15k or 20k miles.

 

[MRiley]

I can get about 12 -13 petty consistently pulling my 28 footer. On a rare trip I will hit 14.



I heard that the 6. 7 wasn't going to get the same mpg as the 5. 9. It sounds norm to me. More displacement = more volume = more fuel used. Also all the new emissions stuff should really pull on the mpg as well.

 

[KBalzuweit]

10 is not that bad compared to what some other drivers I have met are getting. As far as 15. 9 mpg pulling a 35fter, THATS A BUNCH OF BS!! I have ran 1st, 2nd, an 3rr gen trucks and never seen that kind of fuel economy.

 

[Fireman]

I'd say, an honest 10 mpg is not bad. Not great, but nothing to complain about.



One of the biggest factors that affects our mileage towing large campers is DRAG ! Drag affects economy more than gross weight. As you drive faster the effect of drag increases exponentially. Towing a high profile 5th wheel at highway speeds, a reduction of 5 mph could net you 1/2 mpg increase in fuel economy. The faster you go, the more it costs and above 70 fuel economy will start a steep decline. For a really good look at aerodynamic drag get your hands on issue 43 of The Register and read Exhaust notes by Kevin Cameron titled It's a DRAG Slow down to save fuel, just remember, it is dangerous to drive too slowly on our interstates, any speed below 60 isn't recomended.



Another thing that really affects darag on high profile trailers is the shape of the nose. My friend (and former TDR member) Casey Balvert and I have studied this and found that the more rounded and curved the nose of the trailer the better in terms of wind resistance. Flat front trailers (like my Arctic Fox) are really horrible. Casey used to own an American Star, a very flat fronted FW. He bought an Aerotravel III wing and it helped his mileage (only about 1/2 mpg) along with the overall stability of the trailer. When he traded up to a Mountain Aire with a beautifuly curved nose he found that his mileage was the same with or without the wing. Since he makes a couple of 2000+ mile trips a year he had some reasonably sound data.



No longer needing the wing, he sold it to me. As a long time reader of these forums, I had no delusions about the wing and incredable mileage increases. I bought it for a very reasonable price figuring it would be worth it for the added stability and keeping the bugs off the front of the trailer :-laf. In 8000 miles of towing over the last 8 months I was very suprised (and pleased) to discover that we must have set the height and angle of the wing just right. My average economy has increased from 10 mpg (avg) to 11. 4 (avg) exceding my wildest expectations (but still only half of what the manufacturer claims:-laf). With diesel fuel hovering in the $3/gal range the wing has paid for itself already.

 

[Hounddog]

All,

Thanks for the replies. I've since found out more about my friends mpg figures and they are from the onboard calculator which we all know is crap. I've already found out that mine is off by almost 1. 5mpg. The figures I posted for my truck were actual calculatations from gallons filled up to miles driven. I'm not disappointed at all because I have a lead foot and drive in New Mexico at 75mph. So I have altitude loss and mucho wind resistance. Cummins diesels just plain work and I'm happy.

 

[Grizzly]

klenger and JCasper, thank you for being the most honest people on TDR. The mileage you get are the most believable. Ken and I have the same truck (except mine is a DRW), the same 5er, even the same hitch and we get the same mileage. I keep my speed at 65 or less and I pretend that there is an egg between my right foot and the accelerator.

 

[Fireman]

You didn't believe me :{ LOL

 

[JCasper]

klenger and JCasper, thank you for being the most honest people on TDR. The mileage you get are the most believable. Ken and I have the same truck (except mine is a DRW), the same 5er, even the same hitch and we get the same mileage. I keep my speed at 65 or less and I pretend that there is an egg between my right foot and the accelerator.

No problem. I never believe the overhead. It's never correct.



I also never really see over 10-11 when I am towing anything of size. I tow hard and don't drive it easy.



My towing mileage on my yellowstone trip would of actually been a little less then 10. 7 as that is an average for the whole trip. About 4-500 miles of that trip was without the trailer.

 

[Grizzly]

You didn't believe me :{ LOL

I believe you now that I went back and read your post. I didn't read your post before because it was too long. The wing you are talking about, is it a spoiler that goes on top of the cab of the truck? Can you download a picture of it.

 

[SnoKing]

We are on a two month RV trip in the Western States. Highest Mileage was front Tahoe down to the Coast at Bodega Bay. Just under 14. Average is around 12 mpg, combined weight is 19K, with high profile 5er (12'8"). Low was headed West out of Custer SD into a good headwind at 10MPG. Across Montana with a tail wind, I got 13MPG. SNOKING

 

[Fireman]

ROTF ! I guess that was a bit long :-laf



Here is a pic of the wing.



#ad




Not bad for $100. I figured it was worth that just to keep from having to clean all those bugs off the trailer.

 

[Fireman]

All,

I'm not disappointed at all because I have a lead foot and drive in New Mexico at 75mph.

Just so you know ... ...

Trailer Service tires (STs) are only speed rated to 65 mph

Light Truck tires (LTs) speed rated to 85 mph



check your trailer an see what you have

 

[DWeiler]

Front-end like this on the fiver helps too.

 

[icman95]

Need to know more about the wing. Brand/manufacturer name, etc. Tried unsuccessfully this summer to get one in CT. Wings by Taylor from CA was one I called and their closest dealer was 3-4 hours away. They said they'd ship one to me at about $200 for shipping, but that's a bit much on top of the cost of the setup and I'd prefer to see it first. I know JCWhitney has fiberglass ones, but I was looking for metal. Please send info...