Today was my first real test towing...1050 miles on truck. From Canon City CO to Santa Fe NM...over Raton Pass..Interstate all of the way....averaged 6.5 mpg..
My 15 F350 with 4.30 gears averaged 8 mpg for the same trip and seemed to have better power climbing and the boost gage did not seem to be as high...
I am wondering if they need to reflash the truck... how is everyone else doing?

 

Invstr are these hand calculated or what the truck says. Just wondering if it is the truck, may be off?

 

What speed/rpm/gear are you towing in? That seems awfully low unless you're towing at 70 mph. Fuel mileage decreases greatly above 55-60. I know everyone wants to go fast but mpg suffers. I understand you are comparing to your old truck so I'm sure you are driving the same as always but curious to know the speed. The 6.5 seems subpar unless high speeds are involved.

 

Answers are... 48 gal in tank, 323 mile trip, 60 miles from destination fuel warning came on.. 50 miles till empty... got 39 gal of fuel..so hand calculator is 6.74 mpg.

My normal towing speed if the speed limit.. with F350 i would have been towing at 75....with this being new I took it easy and was towing at 65.. should have been better on fuel not worse..same RV, same gear ratio, better? motor performance...

Sadly on steeper sections it seemed to lack power.. The 350 would maintain at least 55 but the 450 dropped to 45 which is about what my cummins would do.

 

I'm puzzled by the difference in climbing speed. I wonder if the transmission shifted differently. At 65 MPH, if your transmission was willing, you could pull at maximum HP in 4th gear (2800 RPM). It could have dropped to 3rd just below 55 to hit max HP as well. What was the engine speed when it slowed from 55 down to 45?

 

You could also switch to manual mode and control the shift points your self but that would take a lot of experimentation to determine best mileage and chances are the transmission actually knows better.

 

It could be transmission programing... but feels more like down on power

 

How much of that could be the de-rate that is done on F450s vs full power F350s? I've always understood that Ford retards the power on the F450s in favor of reliability and longevity.

 

I've seen many videos of mountain climbs with the diesels and many seem to really delay downshifting. On the F450 at 55, you'll spin just over 2800 RPM in 4th and 2150 in 3rd.

2800 RPM (825 ft-lb*2800/5252)=440 HP
2150 RPM (900 ft-lb*2150/5252)=368 HP = 16% less climbing power.
16% is significant, but would almost (but not quite) account for a 45 MPH climb vs 55 MPH.

[Note: 900 ft-lb @ 2150 is a reasonable estimate. We know it's 925 at 2000 and 825 at 2800, just interpolating.)

 

I checked with ford garage today, no updates or anything for my truck...they just said to keep driving it...oh well

 

I have never read that. Please quote it if you can find it. There is a de-rate of power for the cab/chassis models. Maybe that is where you read it?

 

it is only cab and chassis

 

Yes, I was thinking C&C.

 

Surprising that its that much of a difference. Thats discouraging....Wonder if its just not broke in yet possibly?

 

The major mpg swings in my experience have to do with weather. You have any idea if you were fighting a 10mph wind all day?

Also, I'm not sure I believe it to be true, but it's possible that the engine performance will improve as you run it. Maybe see what happens when you've got 10,000 on it?