How you drive can also have a big effect on MPG. Now, I'm not referring to the usual cries of drive it like a grandma,etc... What I'm saying is you have to drive for both the conditions, AND the strengths of the motor. You need to operate the motor in/near it's most effecient "mode" as much as possible. What does that mean?
Well, if you have a V8 with lots of low end torque, and maybe the power curve drops off at a relatively low rpm, then don't rev the crap out of it. Run it between peak torque and peak HP rpm as much as possible.
Same thing if you have a little 4cyl, that makes most of it's power at mid to upper rpm. Don't "baby it". If it doesn't start to "come alive" until 2500-3000rpm, and it's still pulling at redline, then drive it that way. WOT until you reach cruise speed, high rpm shifts, frequent downshifts when needed, to keep it in the powerband.
The SOHC V6 in the Explorers is in between. It does make it's power a little higher up than a V8, so drive it that way, and it will be more efficient than if it you drive like the V8.
Also, keep in mind that an engine is an air pump. It is most efficient at WOT, as a partially opened throttle blade represents a greater "pumping" restriction than a fully open throttle.
Now, I'm not saying you'll save gas by racing from one stop light to another. However, if you'll be able to keep moving long enough to offset the higher initial fuel use of hard acceleration from a standing stop, then the most efficient thing to do is is to open the throttle quickly and fully, until you reach cruise speed, then back off and smoothly maintain that speed. The actual distance you need to cruise before this pays off will, obviously, vary from vehicle to vehicle (as well as with what cruise speed you're trying to reach), but a good guess would be approx no less than 1/4 mile at typical light urban traffic speed, up to a minimum of approx 1/2 mile or more if accelerating to a higher cruise speed.
This is similar to why those obnoxious hypermilers kinda get one thing right, referring to pulse-and-glide, as they call it.