Tune up. New coils, plugs, and injectors. Maybe look into a K&N air intake system and a new fuel filter. Make sure tires are aired up all the way, etc. Other than that, a consistent cruising speed down the highway (65-70 mph) should net you nice results. On my first run I got 17mpg going down I-44 from St. Louis to Joplin. That was a loaded vehicle, AC on, and two buddies at 65 mph. Not too shabby. On the way home it was around 15 mph and I believe that's due to driving back uphill.
My average around town mileage is about 13-13.5 mpg. I have a 26 gallon tank and if I top it off good I can squeeze about 325 miles out of it - and that's with the Low Fuel light on.
I've gotten as high as 18 mpg (which is pretty damn good for a truck rated at a "best case" of 17 mpg) on my way to Toronto with 4 adults and luggage. Tires were set to 36 psi all around and I had the cruise set to 65-70 mph.
Maintenance items (which were mentioned earlier) notwithstanding, the biggest mpg killers on these trucks seems to be 'stop and go' driving conditions, traveling at over 70 mph and of course...being too heavy on the pedal.
If you drive it like you're gas gauge is on "E" and there's no gas station to be seen, you'll probably be as surprised as I was how efficient these trucks can be if you watch what you're doing.
I was averaging between 10.8 and 11.4 in town with my 99 EB 5.4. I put a single Flowmaster on, complete tune up and K/N. I didnt notice any change. I since added 2" and 33,s. I then put the performance tune[Superchips 1715] and I run 89 octane.
I steadily saw the mpg rise and on a trip to Myrtle Beach,SC[roughly 260-ish miles] Combined hwy and two lane roads I averaged 15.7. Running between 55 and 75 with the a/c full blast.
While in MB, I averaged 14.2-14.6. I was blown away.Since I have been back, Im still in the lower 14 range.
I do the numbers on my own and watch the overhead.
"How can you increase fuel mileage in 02 5.4 Expedition?", you ask? Well..., the best method is by not driving it.
Yeah, yeah... I know... That was not funny...
The best I ever got from my 00 5.4 EB was around 21mpg on highway. On the current 04 I've gotten as good as 22mpg. Around town, no matter what you do, it's between 13-14mpg.
Lots of good suggestions here already regarding things to do (tune-up, free flowing intake/exhaust, drafting etc.), but one thing to also keep in mind is do what hypermilers do: use your brakes as little as possible. Especially in city driving.
I try to do that sometimes, but never have enough patience to do it consistently. But I've heard/read that it helps.
The best I have ever gotten was 17.4mpg and that was on an all highway run with the usual stop-n-go for the toll plazas. I had the Expedition filled with gear, 4 people and a black lab. Since then, I have achieved similar results on the same trip. Around town, I am averaging between 12-13mpg. All mentioned tips are excellent to increase fuel mileage. At the time I got the 17.4mpg, I was running load range C tires and had them inflated to 40psi. I had to replace the tires about 5 months ago, and I have done the same highway trip a few times. The new tires are Standard Load all-seasons and I got the same 17-18mpg. Had them inflated to 35psi. I do usual maintenance and the truck is all stock. Basic air cleaner, stock exhaust, no chips or power adders. For as heavy as these things are, I am more than happy when I get anything over 15mpg.
2002 Expedition XLT 4x4 5.4L
Sport Appearance Package
Don't forget alignment. That's a biggie. So, free flowing in, good spark, free flowing out, and a light foot. Anything you purchase to help that will improve mileage. Troyer Performance has some sweet add ons. Under drive pulleys, and the kicker is electric fan.
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