Background - Bought a 2002 F150 FX4 (rancho shocks long gone) in December of 2014 and it had 230K miles on it. Truck has the 5.4L automatic, 4WD, open dif, soft tonneau cover, stock wheels/stock tire size, power windows and power locks, cab and a half and no upgrades that I noticed - basic stock truck. Bought the truck out of necessity for a daily driver in the winter and started tracking the MPGs from day one, tracked miles and filled up at less than half tank for faster readings. Gas station is on my way home from work so not really a big deal.
Started getting 14MPG and noticing that the truck ran cold, the temp gauge would not eve go half way. After the first week and a half I replaced the thermostat. MPGs increased to 16 on the next fill up. Turns out the thermostat was stuck open so during the cold winter the engine never got up to proper operating temp making it work a little harder.

 

After about 3,500 miles had oil changed to synthetic, added a SPECTRE air filter (with GOTTs mod) and a Hypertech max energy tuner. MPGs increased to high 17s.

Driving daily is 70% highway about 25-35 miles per weekday. Highway speeds are 65 on average and city is mostly 30 with stops and stop lights. Not heavy footed but not slow either just normal driving. Winter driving during this time mostly highway and occasional 4wd ON. Windows up and heater on.

 

My 2001 CREW got high 17s on the highway all the time in summer... My "newer" 2002 CREW is lucky to get 16.5 on the highway, constant 60 MPH......... don't know why.

 

Hi Steve, did you notice a difference in the RPMs at the same speed between one and the other? That is strange. I'm also trying to figure out how I get up to 19 sometimes. I don't change my driving habits that much. My RPMs around 60MPH are right at 1500 and I idle (mostly) at 600.

 

after another 3K miles and warm weather starting I turned on my AC a few times for the first time and it blew cold air - BONUS. But I didn't use it much since the weather is nice and cool up in MN. I did let my buddy borrow the truck to move and he turned the AC on during a long haul. when I got the truck back I did notice a new noise that I hadn't before. Like a gurgling sound from the passenger side. A few days later the AC clutch pulley completely seized up and ruined the belt. When I removed it the bearing completely fell apart. I think the noise was the bearing starting to go. During the weekend I replaced the pulley with a autozone one and while I had all the stuff out I removed the stock fan and installed an e-fan I had picked up from CL before for about $20. The E-fan was off a mustang OEM number 1R3H-8C607. After a little thinking and a little cutting of the original shroud I was able to fit the e-fan in there. The e-fan is mounted to the shroud with 3 bolts and I can use the original shroud mounting brackets on the truck. I also bought the e-fan controller from autozon model 733652 for $25 and installed the heat sensor on the radiator. I used a hose and water to clean out the radiator as best I could shooting water from the engine out, that did clean out a lot of gunk. I don't have pics of the fan in the shroud but will get some soon. The wiring was simple, the fan actually has a high and low setting but I only hooked up the high. Once I was done the noise was gone and the e-fan was working. I did blow the fuse twice so I upgraded to a higher amperage one. Good move? maybe not but it is still working.

 

I realized my pictures were not showing up on the posts above because I didn't click "upload"... Yeah... Hopefully it works this time.

 

After the new pulley and the e-fan I enjoyed 18 to low 19 MPG with the same highway driving so I did a few non MPG related things to the truck. New radio double din style that I picked up cheap. The Jensen VX7020 with Bluetooth, backup camera hookup (in the works), CD, MP3, touchscreen and other goodies. Install was simple with the adapter. I also added swing boxes that I picked up on CL for $40 on both. Removed the headlight nipples and polished them. I also cleaned up the rust under the doors. Wire brush wheel to remove the rust and paint then I brushed on some phosphoric acid to treat the metal and then sprayed over with some stock white rust-oleum rattle can. Turned out really nice and has held up for months on one side, I have to redo the passenger side.

 

So after a few thousand more miles on the truck with no issues I started to see the MPGs decrease again. I also noticed that there was a humming sound from the front wheels, sounded like I was driving on off-road tires. After researching this seemed to be a common issue with the 2004 and newer f150s and the Hub that disconnects the CV Joint but they described it more like clicking. During the same time the breaks also started to get squeaky so I decided to tackle that and see what else I found while I was down there. I ended up replacing the Hubs, Rotors and Calipers on both sides. Winter and salt really take their toll on the bottom side of vehicles. Hubs were really rusty. Pics below show the before and after, I did not have the time to paint the one brake bracket but I'll get to it soon, I'm hoping the added paint will keep the rust away. I want to eventually try my hand at powder coating so when the time comes I'll do that on all the parts. During this time I also checked for vacuum leaks and cleaned out the PCV valve with carburetor cleaner... while the paint dried.

 

I'll try to keep posting details on MPG and what helps and what does not. The plan is to re-do the rear brakes soon, change transmission oil to full synthetic and also do both Differentials with full synthetic oil. I'll do recaps on MPG and how the process went for that. I'm currently working on replacing all of the bulbs I can with white LEDs. Looks really good so far and LEDs are dirt cheap on ebay.

 

nice job on the door panels and brakes... My trucks both had 3.55 LS rear axles. Not sure why one got 1- 1.5 MPG better than the other. I have synthetic in the rear axle, new MERCON V in the transmission. I use regular 5 w 20 motor oil, new antifreeze, new plugs at 100K ...exact same tires and rims....... still cant explain mileage.