I mean honestly, i've never heard of this, out of something that isint hybrid. But you know, theirs a lot that I havent heard of that is actually around today.
My brother (never owned a truck in his life) would agree with the O2 sensor swap. He says putting new ones, or something aftermarket, actually helps his fuel mileage. Never said how much, but he said it helps. Now, I think that this is just a load of smoke being blown around. Sure, you'll get some better fuel mileage. But 23 miles to the gallon from just an O2 sensor? I find it hard to believe. He have any other aftermarket parts hes sweeping under the rug?

 

Pretty much x2 for me as well. I live only 6 miles from work, all city driving. My engine temp guage is barely moving off cold in the winter weather. I see just under 11mpg with my 1999 F150 4x4 4.6liter. That is an average. In the winter I am lucky to get 9mpg. In the summer I get closer to 12mpg. On the highway, and I mean 100% interstate driving w/ the cruise set at 70mph I have seen just shy of 19mpg on a tank. That is no city driving at all, just pulling off on an exit to fill up...and flat land. Once I got in to the mountains that dropped to 14-15mpg at best.

Mike

 

I've never figured how they could put those numbers on the new car window stickers. I, too, have seen 8 & 9 MPG, and sometimes down to 6. Stop & go rush hour traffic kills mileage. But I have seen pretty good freeway miles also. When I had stock tires & gears, I got up to 27 MPG, cruising on the freeway @ 55 MPH, for a few hundred miles.

 

Which wires did you replace? -Well, that may be the problem. Modulars don't use plug wires anymore and the 5.4L NEVER did.. Which wires were messed with ?

23 mpg ? That's stretching it, but I put my money on that being correct and very possible. I've made 20 before, well close enough to call it 20 mpg. But man that takes discipline/all e-way/cruise/55-60- mph and Ohio or flat land.

16 is my average tho and I keep my forward O2's fresh. Keep the wires tucked away from the wind/water and road grime, they are sensitive as hell!!

 

It's all in how you drive; I live in FL (true it's flat land here), have an 04 Lariat with a 5.4 L, but since I've changed the way I drive, I consistently get 16 MPG city driving. I simply stopped my heavy accelerating and my, dare I say, "aggressive driving." Keep a light foot on the gas pedal, and look into hypermilling.

 

17 highway on my 01 5.4.

 

i have slowed down my driving and noticed improvements... on hiway i would get 22mpg at 55-60 mph.. but i have just went from 18" wheels to 22" and milage has dropped to 18 maybe 19 at 55mph

 

I have an 07 4.6 and I get 14-16 mpg city w/ a trialer and 22 hwy at 65 mph.

 

02 5.4 here in cali and i get about 16-17 in city driving, easy on the gas for the most part.

 

I got 23 *ONCE* in mine - and its a shortie with a V6 and a stick. Window said 16/20. With maybe a few rare exceptions, the only way a Screw is gonna get 23 is if you get an air bubble in the tank and the nozzle shuts off early, and you do the math for that one tank.

 

I find 23 hard to believe. I have 07 Screw 4x4 and if I'm only on the highway I can get 19-20 running 67mph. Mix of highway and local driving I will get around 16mpg.

 

Me too. 99 4.6 ext cab.

 

Maybe he is running smaller than stock tires and it isnt calibrated and HE THINKS hes getting that.

 

My 98 SCab 4.6, got about 11/ 12 around town and 15 on the highway, when I bought it . After exhaust, K&N drop in, and Ege, it went up to 12/ 13, in town, and 17 on the highway. My new, to me, 2001 Expedition 5.4 got 13.5 on the first tank full, and it is in need of the 100000 mile service. I figure with exhaust and Edge, it will probably be around 14 in town, and 17/ 18 on teh highway.

 

My 08 i get 18mpg highway or town it don't seem to matter.