I call BS on anyone who claims to get 16MPG with a truck identically equiped as mine. I've seen some people make the claim and I just don't see how it's possible. I've gone back to stock tire size (and recal'd the speedo), replaced the spark plugs and the fuel filter. I've cleaned the EGR and the MAF. And what kind of improvement do I get? None! I'm still getting the exact same mileage I was before I did all that. 12.7MPG. And it's consistent. Multiple tanks, varied driving style, everything. This last tank I thought for sure would show an improvement because I drove exactly how you should to get best mileage. Accelerate slowly, stay under 55, brake earlier. I knew what I was getting into with buying a gas hog...that isn't my complaint. I just can't believe someone with the exact same truck can get 16MPG or better. Is there something wrong with my truck? Or are they just lying?

 

Are you running an amp with that pioneer? One huge drain on milage that eveyone seems to forget is the alternator. The rest of the pullys for that mater. I've thought of buying a set of those "underdrive pulleys myself. There suppose to add 5 to 10% hp, which would equal better mph if you stay off the pedal.

Almost forgot the fan clutch. I've heard that one staying locked up really hurts the milage.

 

Yep, check the fan clutch and o2 sensors. Check to see if any brakes are dragging. I honestly don't think that the alternator is going to pull down the MPGs that much if at all as I run one as well. Make sure that your 4x4 disengages at the diff.

I have a 2000 F150 5.4 Scab auto 4x4 3.55 ORP 75500 miles and I get up to about 17 on the highway. If I have a light load and it's covered, I've gotten up to 20MPG cruising 75MPH to Florida.

In mixed driving I only get around 11-13 and towing in the city is around 10 or so. Interstate towing a 12x6 with a quad or two is around 15MPG.

I run Motorcraft 5w30 semi syn in the engine, factory tranny fluid, Valvoline Max Life Dextron/Mercon 3 in the Tcase, and Mobil 1 75w90 full syn in both diffs.

I wouldn't BS you on this as what would I gain by doing so? Frankly, I was suprised by how good this truck does on the highway on fuel compared to my 9-10MPG anywhere no matter what 351W powered 94 F150.

Mike

 

Last time I checked the clutch felt free. I am running a pretty big amp for the subs, but I'm not even running the amp at half what it is capable of. I do know the alternator will eat some power, but 3-4MPG worth? That seems a bit extreme. I swear I hear an exhaust leak somewhere, but neither I nor my mechanic can find one. We'll see what happens when I get those Edelbrock shorties come tax return time.

 

What kind of driving got you the 12.7MPG?

Mike

 

It was a mix of city and highway. Although my kind of city driving I can't really call city since it's usually a good couple of miles between stop signs. Pure highway driving I get even worse mileage. Maybe I should invest in a shell? And an electric fan...etc. I thought a better investment would be the free 400 twin Kawasaki we've had collecting dust in the back shed. But I'm drowning in red tape trying to get it registered.

 

Despite claims to the contrary, I found my bed was a huge aerodynamic drag. I put a tonneau cover on it, and the truck did better - after a year and after a load of dirt I drove it down the highway with the tailgate open (to clean it out just a few days ago), and was amazed at how well the truck was moving itself down the highway (at 75 to 85 MPH speeds). But I have an 8-foot bed.

I put a single cat-back Dynomax system on mine, too. I finally got the thing to 12.5 MPG (as opposed to 11.5), and was impressed - but still disappointed.

I am just about convinced that there is something most of us 4.6 V8 owners are missing when it comes to fuel economy, but I haven't had the time to figure out what it is yet. It's not going to be a PCV valve or something simple to replace. Is it carbon build up in the throttle body, or is it a forgotten about sensor? Is it a design flaw in the computers or is it a timing issue? I'm not sure, but I find it hard to believe these 4.6's got this bad of fuel economy when they were new. The 5.4's always seemed to do as well, if not better, and while this would make sense for an overloaded engine, the 4.6 should easily move the truck without a MPG loss. Anyway, I still have this feeling that most 4.6 and 5.4 owners are missing something in their tune-ups. I'm just not sure what it is.

 

I'm getting about 16.5-17 mpg with my 01 5.4 4x4 supercab. I've clocked a couple trips from st. louis to rolla (~105 miles) at 65mph the whole way at 20.4 mpg. K&N 77 series intake, BBK 75mm throttle body, helix throttle body spacer, and a glasspacked Y pipe exhaust with 75k on the clock.

 

Hmmmm, I drive 80-90 miles per day back and forth to work and I consistently get 19-21 mpg (depending on traffic) with my 4.6L V8 in an extended cab 2wd with stock everything. I get better mileage with this truck than I did with a 3.0L Ranger.

 

OH yea, anybody else watch "Myth Busters"? They done a MPG test with Ford trucks, 2 trucks, one with the tailgate up, and one with the tailgate down. The tailgate up truck went a long ways farther at highway speeds. I still think you'd get better milage around town at low speeds with the tailgate down but trucks have less drag at highway speeds with it up.

btw, you'll also get better milage in the summer with the ac on and windows up than with no ac and windows down.

 

What are your rear axle gears?

 

Could always get an air flow tailgate if that is a concern. One thing is, was your truck built on a monday, or friday? I swear it seems to make a difference on some vehicles!

 

The 35's aren't helping. The taller diameter may be raising the effective gear ratio of the differentials, which should help fuel economy during highway driving on level surfaces. However, the rolling resistance of the relatively aggressive treads, coupled with the heavier wheel/tire weight compared to stock, works against you.

 

Ever notice what directions those thigs blow when you see one going down the interstate? They always blow inwards. I have never seen one blowing out away from the truck.

 

Actually I have never noticed which way they blow. I will have to check it out.