Ok guys, first I understand that my 5.4L is NOT going to get the mileage of a Honda Accord. But I personally think my setup should be getting better than it is.

What I have:
2003 SCREW 4x4 FX4 5.4L
265-70R17 BFG ATs
Air Force One CAI
Poweraid Throttle Body spacer
Hypertech Power Programmer III set on 87 octane tune.

I just filled up my second tank since I bought the truck and I got a whopping 13.10 Mpgs!! Granted I had 80% city driving, but I figured my light foot and these "Aftermarket accessories" would help a bit. I figured I should/could get 15 MPGs in city driving.

What else can I do? I just filled up with putting a bottle of Gumout with Regane, to see if that may help.

I have the Motorcraft spark plugs to change, but have to get time off from work to get it done. I also plan on replacing the fuel filter and PCV valve.

I guess my biggest question besides what else to do is:
Is the throttle body spacer HURTING my MPGS???

I'm not to thrilled about the CAI and am thinking about another. I think I'd actually like a stock setup with the Gotts mod. I don't have the stock hardware as when I bought it it had the AF 1 CAI. (Anyone have a stock setup for a 2003 they don't need or want??)

I haven't actually checked, but tires look to be ok as far as their inflation.

----DirtySCREW

 

instead of a CAI just do the GOTTS mod for like $12, those new plugs will probably help the mpgs too. oh and might want to clean your MAF sensor.

 

How many miles on it? Mine is a 2 wheel drive and I get around 15 mpg city and 17 tops on the highway. I have 137K though and stock plugs, COPs and o2 sensors. If I did some maintenance I may see a minimal improvement but I drive 80 mph on the highway back and forth to work so it is unlikely to improve by much. I could probably get close to 18 highway if I went 65 but life is too short for that.

 

She's got 137,750 on her---DirtySCREW

 

Well 13 city in 4wd may be all you get. The throttle body spacer is useless but if you don't feel like removing it you aren't hurting your mileage any. Do you know what gears you have? Mine are 3.55 but you may have the 3.73.

 

Remove Brick from bottom of shoe...

 

I'm not sure on gearing...I'm thinking 3.55 as well as it doesn't get-up-and-go like my Yukon which DID have 3.73

No brick here----I think I "got down on it" once or twice. I'm driving for economy!! I don't jack rabbit starts, try to catch the lights on green....basicly, I'm trying to hypermile in a F150 to get the best possible mileage. I plan on replacing the diff fluid with Royal purple and maybe that will free up a little "drag" since the RP is suppose to be more slippery. Also the transfer case as well. I figure that alone should yield between .5 to 1 MPG. I know my tune up will probably help the most, plugs, PCV, cleaning Throttle body. I'm hoping that Gumout with Regane will help!---DirtySCREW

 

Front O2 sensors could help as well as plugs and a good top end cleaning. I doubt the purple stuff will give you any more than .5 but if fluids haven't been changed it sure won't hurt anything to try it.

 

13 to 14 with 80% city driving is about normal. I get 12.5 with 95% city driving, and that is with these massive 38" tires, 4.56 gears, an Air Force One intake, SI/DO exhaust, and a tune on the computer. And I think that number is fairly decent with my setup. But when I was stock, I was getting around 13 to 14 city and about 15.5 highway. Never saw anything better than that no matter what I tried.

 

Keep your AF1 intake, it's the best you can get for these trucks... Get rid of the throttle body spacer.

Your city MPG is pretty normal.

I get 13-14 city/17-19 highway on crappy ethanol blended gas. Also, I'm on 33's.

 

I only get little over 13 city in my truck. I have a 2005 regcab 4x2 with the 5.4 and 3.55 gears. So your 13 in a 4x4 isn't bad at all, my truck should get better what it gets. I take city streets into work and the interstate home and all I can get is little over 13 on average.

 

my daddy has a 2003 5.4 FX4 with 31" tires and gets about 13mpg. your about average so i wouldnt worry about it

 

Mud---can you PM me so I can email you. Thx---DirtySCREW

 

If the fluids have never been changed, or if you don't know what's in there, use 75W140 in the rear, 75W90 in the front, and ATF in the TC. If the rear is limited slip, get fluid that has friction modifier in it, or get a bottle of modifier.

Another thing that will improve mileage is try to find fuel that has no ethanol.

 

yea, I guess I'm just a little bummed about milage b/c my Yukon was 2wd, heavier, faster, and got 15.5-16mpgs in town with me driving in the city. The Mrs. only got 14.5 mpg---she stayed in the gears too long instead of getting thru them and getting into overdrive. I seriously doubt fluid in diffs has ever been changed. My rear diff has a slight leak. I have to order the RP in the rear diff weight (75w140) as its not sold locally that I can find----DirtySCREW