2005 4x4 SuperCrew FX4 with 3.73 LS and 5.4L and only 700 miles on the odometer:

Best highway performance: 16.6 mpg
Best city performance: 12.0 mpg
Overall average: 14.3

I don't drive my truck like a granny, but I haven't been driving it hard, either (since I'm technically still in the "break-in" period).

C-17 Pilot

best I've seen is 17mpg on the interstate when I first bought it.

Since i've had it I get b/t 10 - 15 mpg

Got just over 21 MPG on my last trip across NC. 2005 Super Crew FX4, 5.4L, 3.73 and 18 inch tires (no mods). Gas mileage just keeps getting better as the engine breaks in.

Averaging between 17.5 and 18 mixed city/highway

I usually manage to get about 14-15 city and 18 to 19 sometimes when its just right i get about 20.

My best was my 3rd tank of gas at 11.9 mpg

Its now on its 4th tank and it may be lucky to get over 11.5 mpg.

Too much driving around town. My 4 mile commute on the freeway and 4 miles of side streets each way doesn't help.

I did however get 42 mpg down this really long hill the other day

I have 1200 miles on an '05 SCAB Lariat 4x4 with 3.73LS.

20.19 in the Canadian hills around Wawa in a 04 4.6 4X4 Regular cab with under 10,000 miles on the odometer.

I'm getting 17-18 around town and I just got 23.5 after a 560 mile road trip through the Texas hill country.

My truck is a SCAB 4X2 with 5.5' bed, 5.4l, 3.55 gear.

I get 19.5MPG all day long on the highway with the cruise set at 70mph

I get 14.5 mpg suburban city driving (stoplight every half mile to a mile)

4x4 screw 5.4
5.5' bed
undercover hard tonneau

motor/ecu/intake stock and staying that way

I just did a 2600 mile trip from Tulsa to the North Carolina Coast and back. Almost the entire trip was turnpike or interstate. With 3 adults, luggage, and an infant in the car, I got between 17.1 and 17.8 on my 6 tanks of fuel. I'll post all the fuel data on a later date.

Screw XLT 4x4
3.55 rear
18" Lariat wheels/tires
dual flowmasters
undercover tonneau cover (spelling?)
75-80mph the entire trip

Grim

I have gotten 13 MPG since day one. I just filled up today and had 300 miles on the trip meter and put 23 gallons of gas in the tank. That's 13.04 MPG.

A questio for you guys with the 5.4 and 4x4 getting over 20mpg;

Are you checking the MPG readout computer while on the highway, or is this the average on a tank of gas between fill ups?

The 22.5 on my 4.6 2wd with skinny stock tires pumped to 40psi got was for a full tank of fuel. I'm sure that if I starterd the average MPG compute while driving on the highway and ended the computation before exiting the highway, the mpg would be quite a bit higher than the average on a fuel tank which did involve a bit of stop and go and cold start etc.

Something wrong here, I get about 99 plus on downhills

Mathteacher88, your mileage should come up some eventually, most everyone gets better MPG after they get used to the truck and/or it breaks in.

Some helpful things I've found;
Don't top up the tank. Ever. Three clicks maximum.
Be sure you are taking your foot off the gas when it is coasting. These trucks 'freewheel' that is, unclutch, or feather, when you are going down the slightest grade. Pushing down on the gas at that point just burns more fuel as the engine is 'out of the loop' at this point. This is very apparent with a Scangauge or vacuum gauge. Takes getting used to, then it's great.

Take your foot off earlier on stops. The truck coasts like nothing since the old overdrive cars from the 50/60s.
Pressing just a little lighter on the throttle gets you 99% of the acceleration, at 75% of the gas. This is sorta true on many vehicles, but REALLY true on this truck/transmission.
Cold mileage is very poor, warm mileage is much better. Good reason to group your trips. Always a good idea, but even more so on this rig.
These trucks hate grades. Really. Ask the gas gauge... If there are two ways to get somewhere, skip the one with the long slow grade.

Try coasting it sometime if you have to deal with grades. I don't mean do something stupid like putting it in neutral, I mean just take the foot off and watch how well it coasts down hill.

Cruise is very accurate on this model.
Best of luck, and I hope your mileage comes up soon.
Chris

I use a Scangauge for constant readout, trip readout, etc.
Then always calculate exact on fillup.
I always top up when I put in gas and reset the trip OD, then do the math.

The Scangauge can be off from the physical as much as 1.5 mpg, either way. That matches with actual fillups. Gas expands and contracts by temperature, so you need to do several fillups to get a more exact reading.

Example, my last three fillups, all from just below half a tank, 17.1-17.5-17.7 that’s about 20% freeway, 80% local on each fill.
Note it is trending up. That relates to the fact that the local temperature is dropping to much lower than normal daytime temps.
So I am getting cool weather with hot weather gas. I will drop like a stone when the winter gas gets here in late October.

The actual gas mileage on freeway going down the pass or something, often hits 23-25 for 50 miles even at 70MPH. It of course, reads 99 on the downgrades . Then coming back up it likes to drop to 18-20. Lows of 12 on the last climb.

Going into town, engine cold, I usually average 14-15. Coming back, engine warm, 16-17. If I start it cold in town and reverse the trip, the mileage is also reversed.
Chris

Thanks for the advice...

The $100 to fill up only hurts once a month so... little mileage means little gas.