After the latest flash recall, I went camping with my toyhauler in Arkansas. I averaged 7.9mpg there and managed to squeek 8.6mpg on the return trip. I think that I have figured out something on the 6.4. On th eway back I was really watching the boost gauge. The sweet spot is not speed or rpm related so much as it is boost related. Next time you take a trip towing, try to keep your boost under 20psi and see if it helps.

as someone that doesn't own a diesel, 8mpg sounds pretty terrible.

Well, the specifics of the truck are 4X4 dually with 4.10 gears. The specifics of the trailer are 11k weight wise, semi hilly area of NW Louisiana, and SW Arkansas. I am happy, I could not get any better than that with my 05 F250 with 3.73 gears. (lighter truck, better mileage gearing) and the F350 just is much more enjoyable to tow with.

The new diesels are horrid in compairison to the 7.3l. Thank the govt for that. It was either emissions reduction at the tailpipe or emissions reductions in fuel usage, they chose the first option. It will however get better, much like the first gen emissions cars of the late 70's. Just wondering how long though.

Its always been tied in with driver usage. Our car hauler is a perfect 68 mph vehicle. Go over, 6-8 mpg, stay under, 9-12 mpg.

mrxlh said:

The specifics of the trailer are 11k weight wise,

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And, presumably, a big frontal area....punching a big hole in the air at highway speeds sucks a LOT of fuel, too.

Ryan, I'll bet you'd never get that mileage with a gasser.....Your truck I'm pretty sure comes in at better than 8,000# empty, combined with that 11,000# toyhauler and the topo where you traveled, I'd say ya done pretty good...

john112deere said:

And, presumably, a big frontal area....punching a big hole in the air at highway speeds sucks a LOT of fuel, too.

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Ian, bingo, I have yet to come up with a spoiler that looks good. I would be willing to bet close to 1-3 mpg worth.

Blue Goose said:

Ryan, I'll bet you'd never get that mileage with a gasser.....Your truck I'm pretty sure comes in at better than 8,000# empty, combined with that 11,000# toyhauler and the topo where you traveled, I'd say ya done pretty good...

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Brad, probably correct. Last gas hauler data I had was my 97 Silverado with a 6X10 trailer and 2 Harleys on it. Truck had a 305 in it, from Florida to Milwaukee (HD 100th Aniversary Rally) averaged 10mpg. THe trailer and 2 bikes weighed 2000lbs with no wind drag. (did not have a rear ramp in the air) I also had a 150 qt cooler slap full of beer, and about 1/8th cord of fire wood. on the camping trip. Would have loved to scale it, but none convienent located along the trip. This was also rural 55 mph highys with little towns and stoplights. Figured that interstate same speed would probably net a 1-2mpg increase without all the starts and stops.

blacksnapon said:

Its always been tied in with driver usage. Our car hauler is a perfect 68 mph vehicle. Go over, 6-8 mpg, stay under, 9-12 mpg.

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Correct Vince. This was the first trip where we got a headstart and were not rushing to get there. Same with on the way back. You wont know til you try different things, and believe me with the compounds on the 6.4, the minute pedel movement makes a big difference in boost when towing. I also forgot to mention I was not on cruise. That is a mileage killer.

Ok, another update. I guess 1 of 2 things is happening, as I averaged 8.8 mpg towing to the campground this weekend, and 9.6 mpg towing home. I don't know if its the latest flash (Vince could probably comment better on that) but it seems to be regening a little less which could be the uptick in mileage. I am going to Canada fishing in a few weeks, I'll post my mileage results from the trip when I get back. I won't be pulling the camper, but did pretty much the same trip last year without the camper when the truck was new. I averaged 12.6 on that trup on the interstate between 70 and 75. I really think the sweet spot is 65 mph with 4.10 gears.

1.) the truck is still breaking in. (20k on the odometer now)
2.) keeping the boost 20psi and below is the sweet spot.

I was towing between 65 and 55 mph with 2 short in town stints on the way to the campground. Theory on why its better on the way back, is were not really in a hurry to come home. Therefore I am watching the boost gauge more closely. This trip was not quite as hilly as going up to Arkansas. But still not flat.

Some of the techs might want to chime in on this one.

1900 RPM's 60 MPH, the truck is getting 17-17.5MPG on the lie o meter
2100 RPM's 65 MPH, the truck is getting 14-14.5MPG " " "
2300 RPM's 70 MPH, the truck is getting 12.5-13MPG " " "

I have hand checked against the lie o meter a while back and it seemed to be pretty darned close. I drove through several sections of highway and interstate yesterday traveling from LA, to WI. I was in no hurry and reset the lie o meter at each speed, minium miles was abot 75-100 at each speed two seperate tests on varing terrain. Thoughts, comments? BTW the truck has 4:10 gear in it. Thinking gear vendor unit for non towing trips like this. 17 in the hills of Missouri is really respectable for an 8500# truck.

On edit regens were occuring from 180 to 230 mile marks (used B trip for keeping up with them) It regenned earlier after going 70 than when traveling 60.

that sounds great ryan. the lie-o-meter is pretty colse on these trucks due to the fact the 64 runs a gasburner style program so fuel mileage is calculated instantly.

bowtiehatr said:

that sounds great ryan. the lie-o-meter is pretty colse on these trucks due to the fact the 64 runs a gasburner style program so fuel mileage is calculated instantly.

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you just have to find that "sweet spot" that is in different spots for different trucks.

Those #'s make sense. I got an average(wish I had the "lie o' meter"... darned XLT) of 16.89 m/gal on a recent trip. My speed was all over the range of 65 - 80 though (that's in my 6.0). In calculating the power required to overcome wind resistance, the speed of the vehicle is cubed (speed^3). In my case I'll bet the time I spent in stop and go/ 80 mph mode means that I can do better in the 60 to 65 mph range. May be 18 mpg??? My truck is lighter than yours to at 7,500 lbs.

Frontal area on my '07 is 36 ft^2 so using HP required=speed^3*Frontal area/150000.

http://www.webtec.co.uk/techinfo/equation/eqnfr/eqn07.htm

I get 65.91 HP at a speed of 65 MPH. At 80 MPH the power required is 122.88 HP. I have to double the output of my engine to get an extra 15 MPH.... You have a new Super Duty but the numbers for your truck will not be much different. May be a few more square feet in frontal area...

I found a better way to calculate HP. I am not sure the equation I posted is correct. Here is some better stuff...
http://www.nitrod.com/articles/HorsepowerTA.pdf

Using those equations I get a total of 47 Hp @ 65MPH and 75 Hp @ 80MPH. Same take away though. The extra 15MPH costs almost twice as much in horsepower.

suprdtydvr said:

I found a better way to calculate HP. I am not sure the equation I posted is correct. Here is some better stuff...
http://www.nitrod.com/articles/HorsepowerTA.pdf

Using those equations I get a total of 47 Hp @ 65MPH and 75 Hp @ 80MPH. Same take away though. The extra 15MPH costs almost twice as much in horsepower.

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Awesome link!

Ryan

Ok, truck is definately still breaking in. 13.7 new average for 70 mph on trip back from Canada to Green Bay. 15.3 new average for 65 mph. didn't reset for 60 mph, but sure it probably went up as well.

Wow, that's a heck of an improvement.

Ryan