Ok so I'm sure this has been addressed a million times but I'd prefer not to spend hours searching for the info I need.
That all said, I've got a '02 F150 4x4 FX4 (5.4L) xcab with 83K miles on it. Not to long ago my average fuel mileage was around 14 in town and 16.5 hwy. Over the last few months I've noticed it really seemed to have dropped. The last 3 tanks I've checked it and I've been around 10.5 city and not to much better for hwy. THere are no error codes being thrown, at least nothing that's kicking off the check engine light. I've set the tires air pressure to 42 psi, cleaned the MAF senser, clean air filter. I know that in some rare cases changing the plugs "could" help but I also know that trying to change the plugs on these motors is a real PITA. I'm also wondering about the O2 sensor, but I would think if it were bad it would throw codes?
Anyone have any ideas that would be great, thanks!
Oh one other thing, it's going through about a quart of oil every 2500 miles or so... I'm getting worried that I've got serious issue??

 

Your opening sentence will keep people from answering your question. They feel that if you can't look it up by yourself, they won't do it for you. I'm actually surprised that you are not having your question hammered, like normally happens.

That said. The winter fuel additive mixtures are different than summer supplies, thus down goes the fuel mileage. This is common in cold climate areas, etc. You have no information on where you are or anything, so I can only give you what I know from my area and others I've lived in.

We are already on winter fuel here in Alaska and we are still in the mid to high 50's right now. Way above average this past week. Other than that, general maintenance is what it takes to keep your mileage as high as possible. Make sure your EGR is clean and working properly. Good luck.

 

This has been my experience on many forums. He didn't say can't, he said didn't want to. Too much trouble I expect, like changing out the PITA plugs. No pain, no gain.
I suggest you pull the easiest plug and have a look see at it. You really need to look at them all but one is better than none.

 

Didn't say I couldn't in fact I've spent a fair sum of time digging as it is. I just don't have hours and hours to did through previous posts. I guess I'll have to though as folks on here are clearly to busy to share the information they've been given to assist them during their issues.
I had people would be less douche baggerish and just throw me a bone.... Time is a very difficult commodity to come up with, so thanks for all the help!

 

Do a search for "Ford 5.4 IMRC intake manifold runner control" to learn how to check if a control rod has fallen off. If the rod has fallen off but the actuator still works it won't throw a code but you will get worse performance and mpg. This is because the OBD monitoring is checking the control movement and not the valve movement. (The OBD approval guys at the California Air Resources Board don't allow that monitoring mistake anymore.) The rod can fall off if the bushing fails. The fix is apparently not easy access.
I did my senior engineering project at Penn State on the subject in 1978 so I have a high interest in the topic of intake manifold runner control. In the late 1800's a guy named Helmholz discovered the "resonator principle" where a wave pulse travels from a valve to the open air then back again. He wrote formulas that describe how the intake air runner length could improve flow. This Helmholz resonator principle led me in 1977 to design a crude rpm variable intake runner length mechanism to get natural supercharging using the pulse. Being a poor student I didn't patent the idea. In the meantime engine designers discovered the principle and started to install such variable intake length systems. The Ford system uses just 2 lengths but it works to add power that is beneficial.

 

I stated that your opening comment usually gets 10-20 bitch-slaps before the day is out. You didn't so you really have nothing to complain about. Three of us "threw you a bone" and you only complained about it. Check what we told you, then you can either come back and tell us what (if anything) changed, and we could help from there. What you asked has so many possibilities, that no one can give you a straight answer without you doing some of the things we suggested first. There is NO straight answer for fuel mileage. Air, Fuel & Spark. You have to go from there.