My latest calculation was 14.9. That was driving 333 miles with about 30 or less of them as around town. The rest were pure almost back to back highway miles, driven at 65-70 mpg, mostly under 70.

Ok, some data to help answer the question...

Truck - 03 Exp, 4.6l (with only me in it for the most part)
AF1 intake
TP Xcal 2 running 93 perf tune
Royal Purple last 2 changes
Recently replaced right, upstream O2 (based on weird datalogging record on the Xcal). TP said it might be the O2, or a leaking exhaust manifold allowing more O2 getting to the sensor
Winter gas mix - should lower mpg 1-2 I know, but I've been getting 15.5 consistently even in warm weather. So the 14 ish mpg seems to be the effect of winter gas mix.

Before Mods using 87 gas, i was able to get up to 18 mpg's on the highway. After mods, mpg dropped 2-3 mpgs, but driveability is way better so there is some compensation.

Anyhow, given the information above, and accounting for winter gas, shouldn't I be getting a little bit better mpgs?

any thoughts would be appreciated.

 

Not really, 14-15 seems about right, I think best mpg's are achieved at 88 km/h I believe on my truck, 2000 f-150, so yours should get best around there too. Winter time is not the greatest for mileage, how bad? keep an eye on it. Try a spark plug change if mileage is close to indicating it's time.

 

Problem#1: Problem#2: AF1 intake - Clean your MAF sensor

Problem#3: Problem#4:

 

Awe c'mon - you know what I mean - 60-70 MPH!

Agree about the O2 - need to relog and see if the peculiar action is still there or if the replacement o2 fixed it.

Cleaned the MAF. No problem there.

Driveability is not a problem! Even my wife notices the difference and likes it

I'm just thinking that the mileage is a little too low. I go outta my way to take care of this thing. I even play classical music on the CD player - known to help children and plants grow better.

It should be alittle better I think.

Any OTHER thoughts out there?

 

I would agree with blue. I have a 97 F150 4.6 that is completely stock and get around 12-14 in the winter. Last summer I took a short trip to St. Peter, MN and got around 19.5 after killing off the tank. By my educated quess I would have to say that I was getting about 20-21 on the highway with the cruise set at 65mph.

 

LOL.....10-12 here, and it runs fine

 

Sounds about normal to me.

I get around 12-14 city and 17-18 highway. These Ford V-8's drink fuel like an alcoholic

 

Keep in mind that Waterman is saying that he's getting only 14.9 and that it's about 90% highway . I was getting 16 on the highway and about 14 or less around town . Thought it sucked so I took it to my mechanic . He reset the TPS to spec , cleaned the intake , found a couple poor connections at the PCM , corrected them , also found that #'s 3 & 4 had something wrong with the connection at the COPS and corrected them . My first tank after the corrections I got 13.8 , no change . Next tank 15.6 . Next tank the same . Guess the computer took a little while to adjust to the corrections . the driving was nearly identical because I drive back and forth between my construction sites all week . My opinion is , if you're only getting 14.9 on the highway something is wrong . You should be getting 18 . If you're the mechanic try checking the things my guy did . Worked for me .

 

Here is some real life up to the minute experiece.
I run an EDGE tuner with the PID monitors.
Gas is CITGO 87 winter blend, oil is 5w20, rear is 3.55, tires 255/70/16, one passenger, little extra load..
Run through the mountains on varying terrain.
Zeroed the monitor ave mpg.
Drove by watching the instant mpg readings as well as other selected PIDS.
This causes you to keep taking throttle off where you don't need as much.
Showing we all tend to use to much throttle.
Results was as high as 19.3 coming out of the mountains, in 30° temps and speeds of 55 o 65 mph.
Just as soon as I get back into town the ave begins to drop fast such that I ended up at home with an average of 18.4. The hill I have to climb killed several tenths off pretty quick.

Around suburban running, it's 13 to 14.5 99% of the time.

So there is a represenitive of what the average truck will get.
Bottom line is it takes a certain min amount of power to move a 5700 lb load over the road with the least throttle opening.
A 4.6L at 1700 rpm +/- just has not enough torque output to have any real throttle response. That being said, you open the throttle to accelerate the truck and it doesn't move out very fast but the fuel is still being used up at a greater rate even though you not accelerating as fast as you think you should.... good by gas mileage. That's the way it is and no fancy air intakes or exhaust etc will help very much because it's not a question of air or exhaust flow at such low RPM's. The stock hardware is more than adiquit at these running levels.

 

That squares real well with my experience . Last time I took a real road trip and the truck was in good tune I managed 18.3 . Two adults , two children , gear stacked up above the bed a little , mostly hiway with 50 or so miles on gravel roads at 25-30 mph (went camping). Same engine , gearing and tires as Bluegrass . Last time I went on a road trip and it wasn't in good tune I was lucky to get 16 . Thought something was wrong , and it was !

 

How many miles are on your truck? Your cats are probably getting clogged. I gutted my cats, and my highway MPG at 75 - 85 MPH (with a majority of it being at 80) went from low 14s with cats to 15.6 MPG on my last tank. Running 93 octane on my custom Edge tune.

 

sounds low to me... I pulled off 19.2 over around 350 miles, maybe 85% highway, and had three city races too, oh and on winter gas 65-70

 

i have 4.88 gears and 35" rubbers, i range from 12-19mpg... all depends on my foot trying to get that 4.6 to move the monster and what speed i chose.

my speedo says 80mph and i get 14mpg~
70~ i get 15-16
and so on, around town (usually on it like a pig) 13.

i have seen 19mpg while cruising behind a bus at 70mph on speedo (65mph?)

 

Sounds like my truck needs a checkup.

I have checked codes w/ the Xcal2, but I am just a novice at this stuff. Could be something completely different that I am missing.

14mpg driving 65 w/ just me seems too low, especially w/ a few mods for better driving/hp.

Or, the mods give more hp and I loose mpg! and I may have to live with that