The 2004 is larger and heavier than the 2000. Do they both have the same
rear gears? Are you sure your driving styles have not changed becasue of
different preceived dynamics (maybe the 04 is quieter and smoother, so you
unconciously accelerate harder)? How do you check your gas mileage. One tank
averages are notouriously inaccurate. The on board computers are not
particualrly accurate either (my Expedition's onboard computer over
estimates the mileage by at least 1 mpg, My Mother's Grand Marquis computer
always underestimates the mileage).

The EPA estimated a 2000 V8 AWD Explorer at 14 city / 20 Highway. A 2004 V-6
4WD Exploer is rated at 15 city / 20 Highway. It seems to me that, the 2004
V-6 should get the same mileage as the 2000 V-8 all other factor being
equal. However, all factors are not always equal. Since the 2004 is heavier
than the 2000, if you tend to accelerate briskly, you could expect the 2004
to get worse mielage. Likewise, since the 2004 is larger, it is likely to
get slightly lower mileage at higher speeds.

2004 V-6 4x4 - 210 Hp, 3.55:1 Rear Axle (std, 3.73 optional); 4480 lb curb
weight; .41 drag coefficient; 36 sq ft frontal area
2000 V-8 AWD - 215 Hp, 3.55:1 Rear Axle (std, 3.73 optional); 4113 lb curb
weight, .xx drag coefficient, 33 sq ft frontal area

Ed