My 06 fx4 has just about 128k on it. I'm getting on average 12-13 mpg combined. Recently in the past month I've installed the 2.5" leveling kit, replaced all front balljoints, replaced all the sparkplugs (none broke), changed the rear differential fluid, changed the oil, new fuel filter, new air filter and a new fuel pump driver module (im probably missing a bunch more) What else should I do for preventative mantinence and to improve my gas mileage? Also the engine is still idleing a little rough. Do the 5.4 3v motors have replaceable pcv valves? I can't find a definate answer anywhere.

 

Anyone?

 

from what i know, the leveling kit affects some how the mpg a tad. transmision flush every 30k. you can remove and clean the MAF in the intake. you can use any carbon cleaner or inyector cleaner, that could help, and if not, is cheap to do. check the parking brake in the rear, sometimes it locks, that adds friction and eats mpg. i guess tire alignment is done and if you interested in mpg, you must likely already have highway tires instead of off road tires.

 

Check out the maintenance section of this. The 5.4L does not have a replaceable PCV valve as it is built in, this is why it's crucial to run a quality oil as these motors tend to be varnish monsters. After cleaning my TB and intake manifold on my new truck, I've decided to get a catch can to add to it. That's just me though.

https://www.f150forum.com/f2/ultimat...133049/index3/

 

I've also cleaned the maf, throttle body, have gotts mod, I use Mobil 1 full synthetic with a motorcraft filter, it just isn't adding up that I'm getting 12-13 mpg and yes, I do know that I drive a truck. But still. Also I have an edge evo on tow level 2. I'm going to check on that parking brake issue. How could I determine if it's sticking?

 

http://ww2.justanswer.com/uploads/er..._vibration.pdf

 

Front lift,tuner. your going the wrong way for good MPG

 

Did you replace the boots along with the plugs?

Also, good to change the coolant every 5 or 6 years. Coolant becomes corrosive over time.

 

No I didn't do the boots. I probably should've done that but it's pretty expensive at $44 each

 

Calculated it again. I had put the truck on the stock tune, filled it up, drove about 87.3 miles and filled back up again using 8.292 gallons. That only equals about 10.5 mpg?!? What the heck is going on here? HELP