Thread: 2003 XLT FX4 Supercrew Gas Mileage

I have a 2003 XLT supercrew with the FX4 off road package with the 5.4L V8 and automatic trans that I bought back in February about mid way through the month. I just got my 10th tank of fuel today. All I have done is 2WD driving only, about 50/50 mixture of city/highway driving. My first tank of gas was 14 mpg, after that every tank has been between 11.5-12.5 mpg with a 10 tank average of 12.3 mpg. Is this typical mileage or am I short a few mpg. The truck has 177xxx miles on it and runs like a brand new truck. No clue when any maintenance has been done, other then I did an oil change shortly after buying it. If I am short by a few mpg what do you's think the best way to increase it without breaking the bank (I'm on disability, and am low income and can't really perform much work myself and have to have a shop do most of my work for me.

General thoughts here, air filter changed, MAF cleaned, have the plugs been changed and gapped correctly, With my 2005 I averaged around 14 MPG.

Had a 02 fx4 crew cab 5.4 with a 3:55 rear end. Only put about 30k on it but did due the plugs. Your right about where I was. No change after my tune up. Never added anything like a lift, winch. I did put E rated tires on it which are heavy and lost about .7mpg.

Best tank I had was 17.2 that was sea level cruise at 55 for 200 flat miles.

Couple things to check. 1. Is everything stock? 2. Routine maintenance. 3. Where do you live? I'm in Colorado which 85 octane is standard, ethanol is mixed into it, more so in winter. 4. What grade of gas do you use? Premium? Does that station have seperate hoses for each grade? If not there will be a lot of residual low grade diluting the premium.

Honestly I've done about 100k on two different 5.4 2valves in work trucks. Good motor for reliability, the transmissions were never geared to optimize it's power, all this leads to poor mpg and weak accerlation (at altitude). Also I have driven many and some just came off the line better.

Oh and almost every car I've owned got it's best on the first two tanks, Murphy's law?

I live in southwestern Illinois (right across the Mississippi River from St. Louis). I use the lowest grade fuel which is 87 octaine. No most of the gas stations I've used only 1 nozzle for all the grades. Everything is stock, except for a side mounted toolbox on the bed of the truck.

I would top off drive about a 100 mile loop at 55-65 mph in ideal conditions. Top off again at the same station, same grade. Then hand calculate. Let the pump click off, don't force any more after that. If no severe heat, wind, bad traffic etc you should be about 15-16 if you have the 3:55 rear end like I did. My window sticker said 12 city, 16 highway.

For comparison the testing standards back then were different than today. Only compare similar trucks from 2000 through 2003. Before 2000 they had different heads, 04 started the 3valve 5.4 (04 heritage was a carry over old body style and motor)

My 2011 has a mpg graph, more bars = more efficiency. Getting up to speed quickly ( not racing ) then cruising does better than slowly getting to speed. If you watch your rpms you'll see it staying at or above 2300 for a while. My guess is that burns more than a quick 3500 rev to hit 40mph.

I don't speed much but if going 43 in a 40 drops me in a higher gear lowering rpm by a few hundred, I'll do it.

You said that you would need a shop to do most maintenance. Don't let them gouge you for a fuel filter. I had quotes over a hundred dollars. Ford part was 20, fuel line disconect tool kit 10. Process was simple. Pull pump relay, open filler cap, park on ramp so minimal fuel comes out of the line. Ideal with a quarter tank also to minimize leaking. No its not in the tank, shouldn't be charges for that.

Originally Posted by T.C.

I would top off drive about a 100 mile loop at 55-65 mph in ideal conditions. Top off again at the same station, same grade. Then hand calculate. Let the pump click off, don't force any more after that. If no severe heat, wind, bad traffic etc you should be about 15-16 if you have the 3:55 rear end like I did. My window sticker said 12 city, 16 highway.

For comparison the testing standards back then were different than today. Only compare similar trucks from 2000 through 2003. Before 2000 they had different heads, 04 started the 3valve 5.4 (04 heritage was a carry over old body style and motor)

My 2011 has a mpg graph, more bars = more efficiency. Getting up to speed quickly ( not racing ) then cruising does better than slowly getting to speed. If you watch your rpms you'll see it staying at or above 2300 for a while. My guess is that burns more than a quick 3500 rev to hit 40mph.

I don't speed much but if going 43 in a 40 drops me in a higher gear lowering rpm by a few hundred, I'll do it.

You said that you would need a shop to do most maintenance. Don't let them gouge you for a fuel filter. I had quotes over a hundred dollars. Ford part was 20, fuel line disconect tool kit 10. Process was simple. Pull pump relay, open filler cap, park on ramp so minimal fuel comes out of the line. Ideal with a quarter tank also to minimize leaking. No its not in the tank, shouldn't be charges for that.

Great post


Lit up by F150leds.com. ...and fine tuned by the best 5startuning!!!