i've got a 4.6 L.....i get 18 consistantly.....20 on highway....all the time

 

01 F150 4X4, Auto, Lariat, Stepside, bed cover, cat back single in, dual out 40 series, 285/75/16 tires, 74,000 miles. We get 15-16 constant higway, 75mph, unloaded and 14mpg in town. This last weekend we got 14mpg towing empty 18' car hauler, 12mpg towing car trailer with 69 Mustang coupe at 55mph in Ca.and then 10 mpg when I got to Az. and moved up to 75 mph. Real impressed with the power thru the mountains also.

 

2001 supercrew, 4 x 4, 5.4L, 3.55 gears, factory 265-17 tires. 15 MPG highway when its 40 degrees outside and 16.5 MPG when its 90 degrees outside. all at 65 MPH

 

13.5-14mpg avg w/ 50/50 mix city/hiway

17.2mpg on hiway (avg 65mph), 330 miles fill up to fill up, on most recent trip (1/1/06)

2000 4x4 F150 7700 S/C - 5.4, 4R70W, 3.73s, LT245/70R16E's
86K miles
My truck also has a fiberglass canopy & nerf steps. It has my own custom FIPK, homemade side exit catback w/ no muffler, and a Predator tune installed...

This is pretty much the mileage I've gotten since the truck was new (to me) 32K miles ago. Even with the performance add ons... the mileage only tanks when I rip around with it or tow something over 3000#. Then I've only seen it go to 10mppg with a 6000# travel trailer.

-Kerry

 

A few things, I am feeling the same way as maticuno, I am in no way trying to deny the claims of good milage by some, but i know exactly what my truck is getting and it isnt anywhere close to 16-21 that some are claiming. I own an 02 supercrew lariat fx4 with a 5.4 and I am consistently getting 12.2. I am desperate. I have added a k&n, no change. It seems regardless of what i do there is no change. Im getting desperate.
I hear people talking about cleaning the intake, how is that performed?

How do I check what type of gear ratio I have in the rear end?

I have also thought about getting the tranny fluid changed. Does anyone know an approximate figure as to how much it cost do have this performed?

I told my wife tonight I love a ford but so dissapointed in my truck I dont know what to do. Please someone give me some direction.

 

Would replacing O2 sensors make any difference at all? Because that is about all I have left to replace. I'm working as much overtime as I can in preparation of some huge expenditures in trying to get this right. I guess I need to change my signature a tad. As stated in my first post I dropped the tire size from 35's to the stock 31's. I wish I could drop off the cats and go to a single system, but that is illegal in Cali. Damnit!

 

We have threads about cleaning MAFs in this and the 4.6/5.4 forums.
The gear ratio is a code on the door sticker that you can lookup in the tech articles here at FTE or look at the tag hanging from the rear diff, bottom line first 3 characters (1st one may be under the mounting bolt..it's gonna be a 3)
Transmission fluid is not going to improve mileage that much to make it worth your while.
Replace an o2 sensor only if it's bad (which would give you a code and a check engine light).

I'm going to put this out there again... not all engines are going to get the same mileage, even if all the options were the same and you drove and treated each the same. You could baby these things and some of them will get 15, some 11, and every number in between. It's not magic... to some degree it's luck that you get the right engine, the right operator, the right options, and the right conditions that give good mileage.

-Kerry

 

...At highway speeds.

 

I'm not sure what your omment is, but yes, at highway speeds (65 I think) on a closed course race track. Evedently a truck creates a clockwise vortex (is why the leaves blow in the sliding rear window ) in the bed (with the tailgate up) that allows the air to pass right over the rear.

 

I get 99.9 mpg in my '04 F150!

Really!

That is if I reset the mpg display going down the 8% grade not far from here!

Sorry couldn't resist!

 

Well, I'll add in all my specs I can think of. I have a 2003 XLT SuperCrew. 5.4L. Stock air filter. Truck came with some Flowmaster SIDO exhaust. Not sure what model though, since I bought the truck used and it came with it. I don't have any aftermarket computer programmer. Truck is at 23k miles.

Run stock Goodyear Wrangler tires. I have a 3.73 open differential.

Around town in the winter mileage is 12-13. Around town for me means below 40mph usual smaller town traffic. In the summer without the warmups, it'll go from 13-14 in town.

Interstate at 75mph is 15-17, mostly depending on wind regardless of weather. But it will only top out at 17. I still get 17 max on the 65mph state roads.

I have a Coleman/Fleetwood pop-up camper. It's 2500lbs dry. I suppose it's about 3100lbs loaded. I run 70mph down the Interstate towing and I leave overdrive on. The truck almost never downshifts. But I still get 14-15mpg with the camper.

 

only reason i was thinking about the tranny fluid replacement was because of reading on here. I read that it could possibly help because it might help the power reach the rear wheels. Just a thought.

One other thing, The O2 sensor, could it be possible that they are going out but are still reading enough to prevent the Engine Light from coming on? The guy I bought the truck from said he got 16 regardless of how he drove the truck. I may have to call bs on that unless something has changed.

Or he has no real clue as to how to check the milage.

 

OTwo - I think anything is possible. Did Ford not build something to the correct spec, or is something not throwing a code at a level a used / worn engine should be throwing one?

I remember the problem all the manual tranny guys had with the EGR flow once the old inline fuel-injected 6's got worn. A new EGR was not the fix. Putting a restrictor plate was the fix. Ford spec'd the old 400cubic inch (or an engine about that size) EGR for the six, and this posed problems later on. Experienced Ford mechanics knew lessening the flow was the fix, but that never got out to the general public. I wonder if my last truck was sold to me solely because it wasn't running right? Thank goodness for the FTE boards and people willing to get their hands dirty. The truck ran strongly for many years afterward.

I think that we're starting to finally get enough guys who aren't willing to say "That's how it is" with this MPG problem and, with some trial and error, we may get to the root of the problem. A well-runnng, good compression 4.6 should not be getting a regular 11.5 to 12.5 MPG. And it obviously isn't a problem that a easy-to-put-on aftermarket item is going to fix (i.e. induction, exhaust, etc.).

After a while enough posts of owners trying - some of which are trying hard and driving the right way - well, it's just telling me that we're identifying a problem that probably can be fixed. We just don't know what it is yet.

The computers rule these vehicles, and if something is wrong with the computer settings then we may never find the problem. Ford won't help us find it as they want us to buy new trucks.

If it is a part that needs replaced or cleaned, we may eventuallly figure it out.

Best,

GD

 

Wartch where you go when watching the tailgate at highway speed, heheh. How about the fuel blend for the gas station your buying gas at? Try different stations, they might have blend issues. Just a thought.

Dave P.

 

I get 13.5 towing my boat at 75mph. I do too much local driving to get a good reading around town. City mpg goes to chit no matter what you're driving.
Here's the boat.