I've gotta be honest, so far, i'm impressed with the overall ride, shape, vehicle appeal, and pretty much everything there is about an expedition, the only thing I noticed so far, is the fuel mileage is the worst i've ever seen for a short full size vehicle with a mid-small sized V8. I've got a '99 expy 4x4, with the 5.4L. It's been cold lately, but I don't give that too much credit. So far, I've taken it on a 62 mile trip (1 way) (the same trip i've gone in every other vehicle I've had for aeons of time now) and the fuel mileage is horrific, highway or otherwise. I just got this used vehicle last friday, and while I know someone will respond by telling me I just haven't had it long enough, I'm not a complete boob. I've done as much research as I can so far (didn't come with a manual) and have found that the fuel tank should be approx 30 gallons. On my first fill up so far, I had 177 miles and took 16.97 gallons to fill up from that point. That comes out to a little teenie weenie over 10 MPG. (10.43) to be exact. I'm continuing to monitor this as any normal frustrated (or otherwise) individual would do, and it's not averaging any better. Next fill up is probly going to be tomorrow or the next day. In any event, I'm going to check the plugs, etc and probly replace them soon enough. By the way, the vehicle has 65k on it. Any aftermarket or other items that could raise this? It's not driven hard, and most of the time never goes over 2k rpm also. Having just come from a full size suburban with a 350 ('97 model 4x4 also) and attaining a minimum of 15mpg with it, I must say SO FAR I'm pretty dissapointed. I am hopeful that I can find something wrong with it that will improve its performance such as plugs, or fuel filter etc... I will get to all that very soon. Any tips, tricks or other fancy ideas? We were looking at getting an excursion with a V10, and if my mileage doesn't improve, I might just be wishing I'd have gone for the extra muscle for about the same or - 1 or 2 mpg for that much more power if I can't get the economy up some more. Apologies for such a long winded schpeel however, I read the post about 2 or 3 posts ahead of mine about economy and was going to ask what most people are getting on thiers. Seems to me a 5.4 being a relatively small v8 should be getting better than 10-12 mpg w/o towing anything.

I'll listen to any and all Ideas, I'm used to my diesel and slightly older gas engines, I'm not totally farmiliar with the 5.4.
Thanks for reading the garble above!

 

Welcome to the board! Here's a few items that could help your mileage:

• Spark Plugs. Ford says they'll go for 100K, but 75K max is more realistic.
• O2 sensors. HUGE effect on the gas mileage. I'm talking 2 - 3 MPG here. They will work for quite some time, but as they get gummed up, they read the mixture wrong and you end up dumping gas.
• Tire pressure. Ford specifies 30F/35R. I run mine 35 all the way around (some guys here don't like it; they find that the steering gets squirrely.)
• I've found that the Lucas Upper Cylinder Lubricant (available at most parts stores - it's a tall, slender bottle) makes a difference (it supposedly cleans and lubricates the fuel system; the truck does seem to run better after dumping 2 bottles in there every oil change).

I'd look at your O2 sensors first. Then go from there.

XXL

 

Change the fuel filter as well

 

Poor mileage is typical with these trucks, especially the 4x4's. Some with claim exceptional numbers, but the majority are poor. I've had my truck 3 years and get 10-11 mpg city and 14.5-15.5 mpg highway. Adding a superchip got me about .5 mpg increase.

 

With your truck with moderate driving attitude and good maintenance you should be getting about 12-13 in the city and 15-16 at steady legal speeds on flat ground with no head wind. Cold air increases mileage on longer runs of 20 or thirty minutes, decreases it on short runs of a mile or so.

 

Is this a custom chip that plugs in or is this with the handheld unit that you manually reprogram? Are you using it with the higher octane then?

 

I have the exact same truck with 77k on it. I got 15.2 driving 300 miles at 80 mph yesterday. I get 12 around town in traffic. The 4x4s just suck gas.

 

It's the Superchips 1715 tuner. Yes, I use 93 octane. I bought it for its performance gains/scanning capabilities more than for improved mileage.

 

My 2 cents: all other issues being equal, it all boils down to engine displacement, final drive ratio and road speed. My stock '02 Expy with 4.6L engine, 3.55 rear end and cruise control set at 63 MPH (about 1750 RPM) gets 19+ MPG on a 150 mile interstate trip. Road speeds above 65 MPH REALLY suck-up fuel. I don't even want to talk about city mileage in heavy traffic. In my opinion, aftermarket intakes, performance chips and free-flow exhausts are an expensive undertaking with only minimal increases in fuel mileage. Especially with at $2.++ per gallon, we all must realize we own a 5000+ lb vehicle with the Cx of a barn door. As for spirited performance, I leave that to my three sportbikes. For my Expy, I drive that like an old man (matter of fact, I am an old man).

 

Yes you are right...can't get better bang for the buck than a sport bike for speed. For the price of a supercharger, exhaust, etc you can get a bike that is probably faster than any expedition at any price.
Then the dirt bikes for the off road is the same. I always laugh at the guys going 3 mph and then getting stuck when I go wissing by them on my XR650.

Now I just got to get me another gsxr750 to replace the one that was stolen last year...

And the expy is totally able to tow these so I think I'll just put the money into other toys.

 

My 2003 with the 5.4 has averaged between 11 and 12 MPG since I got it new....just seems like that's what it is going to be....