I average 13 anyway I drive, of course I never drive slow.. it is probably 50/50 freeway and city. I have the FX4 3.73 LS 5.4. Towing my 2 waverunners and the bed fully loaded for 300 miles averaging 75-80 mph I still get 12.5-13 mpg, I even got 14 one trip. Hopefully when I get my superchips and intake it will go up, right now I just have a magnaflow exhaust.

 

It sounds like you want to know what makes a 3.55 different from a 3.73. I'll give it a shot, basically the shaft going into the 3.55 differential has to turn 3.55 times for every 1 time the tire turns and the 3.73 has to turn 3.73 times for every one time the tire turns. This means you get more power strokes from the engine with the 3.73 than with the 3.55 which is why the 3.73 is better for towing. Having more power strokes with the 3.73, one would guess the gas mileage would be worse. From what I have heard the 3.55 and 3.73 trucks get the same mileage, so long as they have a similar setup, of course.

 

In my E-150 van 4.6L 3.55 regular axle the no tow mileage was best at 75 MPH (16-18mpg). If I went slower the mileage would go down. I know it sounds wrong but after 65000 miles of which 40000 were highway miles that is what I came up with. When towing with the 4.6L, 3.55's the mileage was terrible (10-12mpg) because I would drive slower and the engine would never keep up the RPM's and was always shifting in and out of OD to the point where I could only tow with OD off. For this reason in my new 04 Screw, I went to the larger engine and the 3.73 rear end. I test drove an F150 Screw with a 3.55 and the revs were about 200-250 lower at 65 mph than with the 3.73. The 3.73's and the 5.4L turns about 1950rpm at 65 and stays in OD with plenty of pull. I can even accelerate while climbing hills without the tranny downshifting. My full size travel trailer only weighs 2000 lbs but the frontal area is probably the biggest drawback to the mileage. As I have said before "For now, I love this truck"
Rick

 

I purchased a 04 Screw 4X4 Lariat about 2 mos ago. It has the 5.4L w/ 3.73 differential. The dash readout says it gets about 16.5 - 18mpg on interstate at 72mph. However, most of my driving is interstate and I have calculated about 15.2mpg. Have put about 2500 miles on truck so far. Excellent truck! It came w/ towing package but have not towed yet, but plan to very soon. Wondering if K&N filter would improve mileage or running a semi synthetic oil?

 

I have the K&N filter, and have not seen any difference.

I check evry tank with pen and paper.

 

I recently installed the K&N Air Charger. I may have seen a mile per gallon increase. I am currently getting in the 13.8 area with all kinds of driving. Before the K&N, I was getting about 12. It may be just the engine finally breaking in as I am approaching 10K miles. These people that post on this site that say they are getting 17-19 mpg are probably doing drugs. There is no way this truck that I have would get that kiind of mileage, even if I towed it! The K&N, due to the noise it makes when you gas it, will cause you to be more aware of the gas pedal. In my case, I hear the noise and back off. So, I guess it is helping the mileage in that sense if nothing else. As far as performance, it is a little better. You really have to stomp on it to see the benefit of it. Probably wouldn't invest in the AirCharger again knowing what I know now.

 

hello, 2004 screw lariat. i was getting 15 mpg in town and 21 on hywy, then they changed the cluthes in the rear end because they were chattering. they said they were to tight. now i get about 13 and 18 mpg and alot of slop in the rearend. i have to take it back and let them check it again, something is to lose or the transmission is starting to slip. i have almost 11,ooo miles on it now. i haven't towed with it yet but i will soon, i have a 30 ft. camper that weights about 8,ooo lbs. i just want to get the rear end checked before i do it.

 

2002 scab, 5.4 with automatic. After 3 weeks ownership I'm getting about 14.5 mpg. I got 16 on a trip to St. Pete and back running 75-80 except for the construction zones. Might have to get a chip for Christmas, not for power so much as to adjust the crappy, slushy shifting (and to be able to read diagnostic codes). I think it's geared too high because it has to downshift with the slightest pressure on the gas pedal. To accelerate quickly it has to downshift twice.

 

Ok I just bought a 2004 fx4 4x4 last week.
Made a trip to Taos this weekend. This truck has the 5.4 and 3.73 gears. Live in Colorado at 4800 ft Trip down in wind and over Laveta pass made 15.4 mpg.
Tailgate down on return trip and steady speed of 70 mph we made 22mpg on trip home. This is better than my Ranger fx4 on the same trip.
Love the new one.

 

You better thank someone for getting one of the good ones. My truck wouldn't get that kind of mileage if I towed it! I can't understand how the same models are getting such variation on mileage. I have tried to drive my like a sane person through an entire tank and still get the same 11+ mpg. May be the Gulf Coast heat!

 

I have a 04 4X4 S-Crew 3.73 5.4, was getting about 14 in town and 17 on highway until I had the PCM flashed, now it's 12.5 town and 16 highway. I have extra weight, brush gaurd, running boards, bed liner, retrax bed cover.

 

My 04 super crew is getting 12 mpg city havent got to take a trip yet. 16 mpg sounds wonderful but I doubt it. I love this truck traded my 03 explorer for it which averaged 22 mpg.

 

I think it could be the tire size? Mine are the 18 inch upgrade?
The first tank full I got 15.3 but was not sure they filled it up all the way at the dealer ship.. That was the worst it has done. I did make 20.4 when i filled up tonight ready for the 70 mile trip to work tomorrow.

 

o4 screw with 5.4 and 3.55 gears. i finished the first mileage check last week at 3800 miles and with an averace over three fill-ups i got 14.08 mpg. i don't drive this truck to work just around town and cruising on the weekends. about 90% is city traffic. i too have a hard time with the statements of 17-18+ mpg. i even read in one post that someone got over 20. i can't swallow that.

i do wish the mileage was a little better but hey, thats what the sticker said so that's what's to be expected. besides i didn't buy it for it's economic features.
love my screw

 

Better take your truck back! Because 17 to 19 on the hwy is reality. You are taking an overall average, which depends on the terrain, and the type of city driving you do. I suggest you get on the HWY, reset the computer and leave it alone. See what you get at 65mph, for a prolonged period.