Get a performance air filter (K&N, or my favorite, S&B, the latter available
for $40 at www.stylin.com), Switch to full synthetic motor oil, install dual
exhaust (if you do this, make sure it is aluminized or stainless steel.  Your
truck comes from the factory with an aluminized system.  Regular steel pipes
will rust out QUICKLY, from the INSIDE.  some muffler shops will paint the
outside of regular steel pipes, but in doing this, your entire system,
including mufflers, WILL STILL RUST OUT from the INSIDE. If ANY of the
exhaust is bare, untreated steel, mild steel, it WILL rust out the aluminzed,
and even STAINLESS parts FAST.  If you go all-out and get headers as well,
make sure they are aluminized or stainless.  Most are only painted on the
OUTSIDE.  Remember, ALUMINIIZED OR STAINLESS.  I can not stress this enough.
Otherwise, you are wasting your money. As far as mufflers go, Flowmasters are
too pricey.  Get a single 2 1/2 in. inlet/dual outlet Hooker AERO Chamber
muffler.  The one for the 5.4L V8 F-150 costs about $65 (www.jegs.com or
www.summitracing.com) The AERO Chamber Mufflers are about $30-$40 CHEAPER (A
PIECE) than the Flows, will last longer, and will actually work BETTER.
(Flowmasters are good mufflers, but there are better ones out there),
Platinum spark plugs help, as do performance plug wires, Throttle body
spacers, especially ones like Poweraid that have a helix to make the air
'spiral' help out, hi-flow Mass Air Sensors help, hi-flow catalytic
convertors are good, (just make sure the ones you purchase are emissions
compatable for your area), a toneau cover or a flow-through tailgate helps
alot , an electric radiator fan as opposed to a mechanical one help out alot
too, taller tires help, however if they are TOO big, and they aren't TOO
heavy, your speedometer will need to be recalibrated (don't worry, it's not
hard to do), a new O2 sensor helps, a new breather element or a new PCV valve
is will help a little, and if you have a lot of these modifications combined,
a new computer programmer will enhance it even more.  Just be sure that you
don't go Rev-happy, or you will defeat the purpose.  ALL of these
modifications will also increase horsepower and torque, as well as gas
mileage, especially when tuned right (hense how the new computer programmer
helps).  some of these mods are on the less-expensive side, some aren't.
Have fun!

Has anyone added anything to their 5.4 liter Supercrew to significantly change
the gas mileage? Right now, I get 15 mpg.

Thanks,

RayJ
2001 F150 Supercrew