Just went on trip average 18 miles per gallon . Driving 70-75 with air cond full blast and cooled seats running. Trip was 650 miles towing a 10,000 pound trailer back i got 13

 

Given ALL the variables that go into mpg - those are GOOD numbers both ways if you think about it !

these are not the most aerodynamic vehicles going thru the wind ---
find that 18 wheeler going 67 mph and then follow at that speed - it runs right @ 1600 rpms where the max torque is (think that's 65-67 mph?) and that's the sweet spot for this engine...

and get better mpg by drafting 4 feet away from them (kidding of course!)

 

Thats good mileage especially running those speeds. You should be pleased.

 

what kind of trailer on the way back? my flat front 7000lb enclosed car hauler is like a sail. pulls me down to 11-12 from 18..

Sam

 

Just back from my first long tow - 750 miles (of which maybe 30 were without the trailer). No A/C, no major hills or valleys. Trailer is a v-nosed Cargo/Pro car hauler. 20 ft plus the nose, total weight 6500-7000 lbs. Truck was light; just me and an overnight bag. Ran 68-75 mph, mostly in the lower range. Open road mostly; no stop and go. No significant head winds.
Total miles 753
Total fuel 58.7
Average mpg 12.8

Truck has 3000 miles, and is a 2012; replaced the 2008. Both crew cabs, but '08 was a short bed. Both trucks are quiet and comfortable, but the 2012 more so. Really appreciated the much bigger fuel tank in the 2012.
2008 got 10.3 in similar driving, so I'm up 2.5 mpg at this point.

Total happiness

 

up 2.5 mpg from prior is a 24% improvement.. amazing isn't it.

Sam

 

Really is; the 2008 originally got 9.x towing, but after a reflash was in the 10.2 range.
Quite the improvement; will it get better with more miles?

 

I have heard other members here say it improves over time, no idea how much really..

I want/ am hoping for better too..

Sam

 

I only have 2000 miles on mine and have never seen better than 12.9 mpg (NOT TOWING!). Sure hope mine "gets better with more miles".

 

mine seems to fluctuate..

at 1500rpm I get the best mileage, 67-68 mph.. (3.31 rear axle) I haven't had a chance to do a long trip yet..

also, if I start the truck by waiting til the glow plug light goes off, then it seems to behave better..

Sam

 

I've had 4 Superduties (2000, 2003, 2006 and now 2011) and I have never seen the mileage improve with break in. My opinion is that is an old wives tale. Current truck will break 60,000 miles this week and still getting the same mpg as the first week.

I have seen my mileage improve each spring with summer grade fuel and drop off each fall with winter grade fuel.

To the Original poster. You mileage is spot on for I've with several 6.7L trucks that I've driven. 80 mph freeway extended distances = 18-18.5 mpg
65-70 mph extended trip with empty truck = 21-23 mpg

Towing is between 10.5 to 13 depending what profile the trailer has. It seems to be more sensitive to wind drag than weight. I pulled a loaded 4H LQ at almost 16,000 lbs and got 1/2 mile per gallon difference than pulling the same empty shell of a trailer at 6,000lbs. So 10,000 lbs lighter saved me .5 mpg

 

Here is what I get. I keep a log of all MPG and regen and MPG is hand calculated.

Previous truck was a 08 250 6.4l srw cc-->MPG range over the time I had it was 13.5-14 not towing and 8.5 towing and regens (not towing) started out with a 275 interval and decreased to a 150 mile interval.

Current is 2012 350 6.7l srw cc with 2200 miles-->MPG range not towing 16.9 to 18 and 11.5 towing 5er that is 2k heavier than camper I had with the 08 and regens are 80 miles apart not towing. When towing rarely have I seen it in regen.


The towing difference is night and day.

 

WoW. Gland to hear someone that has the same crappy fuel mileage as I do !!! The best I have every done is 13 MPH not towing, 10 MPG while towing a 14000 # 5th wheel.
Now, why is that??

ken

 

I recently did a trip from Houston to Va 1200 miles one way, kept the speed around 75 mph. We averaged 20.1 mpg with 3.31s.

 

I'm getting 16.5 with the cruise set at 65ish. I have 900 miles on it right now.