I just bought a 2004 f150 4x4 with 69k miles on the clock. I bought the truck on sunday and drove it home, all highway miles at 65-70 mph. I filled up before i left and after i got home my hand calculated mileage was 11.8!! I put fuel injector cleaner in with that fill up. I filled up again to day i only had 58 miles and 75% were hwy miles, i put 5.2 gallons in thats 10.3 miles to the gallon! What is going on?? I was expecting 15-18 hwy and maybe 13-15 city. I checked the air cleaner and it doesnt look bad but i ordered a k&n drop in anyhow. I also just changed the oil and like i said before i put some fuel injector cleaner in with the last fill up. Any ideas? What do you all get with your 4.6? The truck runs good and idles smooth so i think the fuel filter is fine. Thanks in advance!
-Jesse

 

Cancel that order. Use a stock paper filter.

I hope you used 5W20 oil and any oil filter except a Fram.

 

I like that K&N Air Filter in my unit. Additionally I like the Flowmaster 40 SI/SO for an exhaust with a 2.5" dia. catback.

One of the best "mileage" aids that can be added to a vehicle is a Vacuum Gauge. Mount one withing eye-sight, and learn how to read and interpret the readings; while driving. Works on all gas vehicles and I promise you that you'll thank yourself later.

 

Neither of which improve performance or mileage...

What size tires are you running and what rear end gear ratio is equipped?

 

It has factory 17s with 255 tires. I did use 5w 20 motorcraft oil and a stp filter. I also bought a fuel filter today but havent put it on yet.

 

Well swap the fuel filters and run another tank of gas to get a ball park estimate. Don't forget that no one is getting good gas mileage during the winter. I'm only managing to strain out 14.5 MPG's, but the 4.30's are mostly to blame.

 

That sounds about right IMO. You could disconnect the battery/ Clean the MAF/ reconnect the battery. That may or may not help. It won't hurt.

 

im getting around 14mpg highway on my 5.4L, 4X4, s-cab, 3.30C, 285/75/16's, CAI, exhaust, etc

so that sounds a bit low in my opinion. i would clean the MAF, throttle body, check the fluid in the rear diff, make sure you dont have a dragging ebrake

 

Thanks guys ill try disconnecting the battery and cleaning the maf as well as change the fuel and air filters.

 

I hope you like cleaning the MAF and cleaning the dust out of your intake tube.

 

I checked today and I have 3.55 gears so......I would expect a little better.

 

Never have needed to clean either oil or dirt out of my intake. My K&N filter was first installed 6 years ago, and I've never had a days problem with my install. My intake and exhaust combo had demonstrated improvement in this vehicle's performance, and fuel economy for my type of driving. So what's your issue?

 

haha im getting anywhere from 10.3 mpg to 13.1 mpg, it varies. :/ never changed the fuel filter or cleaned the maf, hopeful that's not important.

 

^^You might want to clean some of that stuff man...

 

My 4.6L gets terrible gas mileage aswell... like 10 or 11 mpg

But could be because i have big tires!