Yes

Yes. There are so many variables but throttle input seems to have the biggest effect on the gauge reading. I can have a wide difference in MPGs at the same speed on a relatively flat highway. I do most of my driving in the city and can get better mileage than I get at times on the highway, if it is not stop and go. If I drive 40-60 MPH on a flat road with no stops I can get MPG readings of near 30 MPG. At 70-75 MPH I generally get low 20s, but at those speeds the road can have more changes which affect the readings. Overall city MPGs average in the upper teens. Cold weather and stop and go traffic can have a large effect on the city readings. I do have 3.73 gears which could affect the highway mileage some and perhaps benefit city driving. Some others have mentioned sustained MPGs in the mid 20s with the 2.7L.

I have an XLT which does not have a boost gauge standard. Higher trim levels have the boost gauge and I'm sure some have added it to their XL/XLT trucks.

Many of the F150 forum members claim lower MPGs with the 5.0, which seems to be the consensus. The 3.5 Ecoboost is between the 5.0 and 2.7 in terms of mileage. The 5.0 with the 10 speed seems to be a better match than it is with the 6 speed.

A factor to consider is where and how you are driving- Long distances at higher speed would be better with lower ratioo
More stop and go low speed- somewhere the higher # ration would be more effiective it would seem

http://www.hotrod.com/articles/1010sr-quick-change-rear-end/

Being able to quickly change diff ratios could answer a lot of questions similar to those in these posts.

In these days of CNC
it would also seems that making
custom planetary gear sets
to go inside Chrysler 46/47/48 OD units
would not be that hard or expensive.

Swapping OD units would just slightly more work than changing
straight cut gears in a Quick Change,
and those extra gears in a Quick change add friction drag, perhaps 2 to 4%.

Thanks, just removed the speed sensor connector on trans checking what you said, speedo still works! It does work off the rearend. 3.54s are going in today!

Update, 3.54 gears are doing fine. Just floats along with very little pedal effort at 50-60 and mph is dead on. Used the state police mile lay off signs on the highway, cruise set at 60, I went 59.96 seconds so that's real close. Filled up today so in about 100 miles I'll check millage, feels like it will be better than 13.5 mpg, hope, hope. Van just feels all around much better, didn't lose any power that I could tell.

Last week I did some very unscientific testing in my '73 Dart (360ci A518, 3.55:1 in a 8-3/4 rear axle).
Tried to measure drivetrain losses with the help of the MegaSquirt ECU and TunerStudio.

Proceded by raising the rear tires just of the ground, put transmission into Drive, throttle it a bit and let it upshift to 3rd and into OD.
Then I let the engine 'idle' with the wheels spinning, making sure the trans stayed in 3rd+OD by looking at the speedometer.

Then I checked the engine-load kPa with TunerStudio.
Did the same with trans in neutral.
Difference in load with transmission in Neutral and in OD was just 5 kPa (30kPa in N, 35kPA in OD).
About 5 kPa drivetrain (transmission & rear axle) loss, at low rpms.

Now I didn't test at higher speeds to see if the difference would be greater.

Interesting test.

Is the kPa that TunerStudio calculates something similar to
“Brake Mean Effective Pressure” BMEP?

With the Oztrip meter one readout is gallons per hour consumption.
When my Magnum 5.9V8 is in warmed-up idle using gasoline without ethanol the Oztrip displays 0.65 GPH.
If I turn the high beam headlights on at idle this will rise to 0.66 or 0.67
If I turn the air conditioning on at idle this rises to 0.71

with such a small change in the numbers one wonders if any of that is voltage drop due to more load?

'kPa' can be seen as an inversed vacuum number.
I could have done the test with a vacuumgauge as well, but the kPa-reading in TunerStudio was more detailed.

100-101 kPa is about barometric pressure = 0 in/hg vacuum = Sealevel airpressure.
50 kPa is about 15 in/hg vacuum
0 kPA is about 29.5 in/hg vacuum

30 kPa = 20.7" vacuum
35 kPa = 19.2" vacuum
So in short, engine vacuum went from 20.7" at idle, to 19.2" with trans in OD.

My MegaSquirt-setup doesn't control fuel yet so I couldn't read any calculated fuel consumption numbers.

Update again, first millage check going from 4.10 to 3.54.
13.1 to 14.6 mpg all around, almost ready for another fill up. I'll average the two this time.

I did 2-hour roundtrip yesterday with my setup (360/A518/3.55); 13.3mpg.
Average engine rpm was 2200-2300rpm between 65-70mph.

Will probably be changing to 3.23 gears soon and try to do a similar test.
I think the small gearchange will be less effective and probably not even "worth it" for mileage.

Last nite fill up, third since change, 14.91. A lot from the 13.1 with 4.10s. 100 miles on interstate at 70-75, rest around town from 25-60. Rpm is about 1700 at 60 iirc (have to use the hand held unit, no stock tack)

Along with the MPG
test how steep a hill you can climb in top gear without a downshift.

Many customers will complain that their vehicle is “gutless” if it will not climb a 4% grade interstate highway hill at 75 mph without downshifting.

Eventhough I live in a super flat country, the previously installed low CR 318 in my daily would have trouble maintaining speed with some gradients in OD with a 3.23 gearing in the axle.
After a swap to a digital ignition with a better curve and 3.55 gears the problem was gone.
Now with the 11.3:1cr 360ci there are no issues at all with changes in road altitude.