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Old 05-27-2011, 10:05 AM   #1
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Question Diesel MPG

We are currently towing a superlite Flagstaff 5th wheel (Tow weight at 8700 lbs) with a Ford 150 (maximum tow rating at 9800 lbs) that has inadequate brakes to handle serious downhill grades (with TH and TBC). We are considering purchasing a 250/2500 diesel and are wondering what the real world is achieving in MPG while towing and when used in regular driving.
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Old 05-27-2011, 11:12 AM   #2
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We bought our 2011, 3500 4x4 Cummins Ram Auto (stock) 6 weeks ago and have done almost 14000kms in it, over half that towing and here's our results, 90% of the time using cruise, except towing on up grades I switch off cruise.

Without 5th wheel:
55-60mph open road 19-21mpg
Urban 14-17mpg

Towing 5er +- 8500lbs:
55-60mph open road 11-13mpg
With head wind 55-60mph open road 9mpg

We have crossed the rockies and done some steep and twisties both with and without the 5th wheel and the mpg difference is almost nothing maybee half a gallon worse.

On all the decents we used the engine brake, barely if ever did we use the normal brakes.
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Old 05-27-2011, 12:02 PM   #3
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With mine towing trailer home from RV dealer best was 14.5 worst 13 that is 8750 lbs trailer 9580 truck. Truck alone was 20 best worse 13.
Old fiver which was only 4000 lbs best 14 worst 13. It had a very flat nose and the wind would kill the fuel mileage. New fiver must be more aero dynamic than old unit of course will see week after next going for a long drive with it and mostly south down
I-5 which is like a wind tunnel that way.
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Old 05-27-2011, 01:59 PM   #4
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With my 2011 2500 Silverado/Duramax/Allison I average about 12 mpg towing. Running empty on open roads or interstate 18-22, but just putting around home (stop & go) I'd say about 15 mpg. For a truck that will pull anything I want to hook behind it.....I'm satisfied.
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Old 05-27-2011, 02:24 PM   #5
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Used to get 13 towing my Flagstaff 8526RLWS 5th wheel at 9100 pounds.
Then I put the bikes on the front of the truck and got 12 on average.

Bikes are now in the shed and I should see the MPG back where it was.

Head Wind in addition to speed is an MPG killer. Best MPG is achieved (for me) at 55 MPH no wind. At 55 I have hit 14 MPG - But I never drive here even if the limit is 55. You will get run over by near everyone.

At 60 - 13.0 MPG
At 65 MPH it drops to 12.0
At 70 it is 11.

Take 1 MPG off if the bikes are on.

Oh, and Ditto - LOVE my truck!
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Old 05-27-2011, 02:25 PM   #6
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I just got a '08 Silverado 2500 Duramax. The first outing was this past weekend. I getting a little over 13 mpg while driving 65mph or less. It drops to 10.5 while driving 70 to 75 mph. The TT and TV total gross weight was 13900 lbs per the scale I used at a truck stop. TT should weigh in at about 6700 lbs. I can get 17 to 18 mpg on the interstates with no trailer.

Just to show how aerodynamics affect things. I pulled a car on a U-Haul trailer that totaled 6100 lbs. The roof of the car was about even with the top of the truck bed. I averaged 15.5 mpg between Dallas Texas and Indianapolis, Ind. I tried to keep the speed at 65 mph or below but would find myself hitting 70 to 75 mph.
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Old 05-27-2011, 03:16 PM   #7
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Obviously head winds and wind resistance is a huge factor in MPGs, I have seen the odd deflector sitting atop a truck but IMO they just don't look right to me, and the hassle of putting it on and off, up or down, do they really work? Even if they did I think I would prefer to pay for the extra diesel.

I put a rear diffuser on my S2000 and I gained about 1.5 seconds on our local track, how about a diffuser on the 5er
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Old 05-27-2011, 03:25 PM   #8
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Used to tow the old fiver with a 1977 F150 w/400 cid v8 was only rated for 185hp and that would only get 12 mpg no matter what that is what it got towing or not I used to call it my gutless wonder or four square engine. 4inch bore 4inch stroke.
It actually did pretty good any hill you would drop to 45mph and second gear. But it lasted for 165,000 miles before I sold it.
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Old 05-27-2011, 06:32 PM   #9
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2009 F-250 diesel with a 33' 5er (silverback). CAT scale shows the trailer to weight about 12,000 loaded.

Only at 23k miles on the truck - getting 17-18 commuting to work, 12-13 pulling the 5er. I have noticed the mileage getting slightly better as the engine breaks in.
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Old 05-27-2011, 07:51 PM   #10
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06 f350 about 14-15 pulling 8500 lb wildwood. Running 17-18 empty.

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Old 05-27-2011, 10:39 PM   #11
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Just remember that if you go with the Chevy or GMC with the Duramax?Allison setup that it has transimission assisted braking...in other words you don't need a 'Jake Brake'!
I get 10 t0 13MPG depending on speed!
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Old 05-27-2011, 11:15 PM   #12
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I have an 08 F250 with the 6.4 diesel. I get 16-17 unloaded and 9-10 pulling the trailer. I'm not real happy with the mileage at 100 bucks a tank. If you're interested in good fuel mileage, go with the Dodge.
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Old 05-27-2011, 11:25 PM   #13
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Quote:
Originally Posted by mike06081969 View Post
I have an 08 F250 with the 6.4 diesel. I get 16-17 unloaded and 9-10 pulling the trailer. I'm not real happy with the mileage at 100 bucks a tank. If you're interested in good fuel mileage, go with the Dodge.
What you said about the Dodge may be true, but from the stats you will be towing a smaller camper.
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