Because they can sell the V6 version for less. There is very little
difference is weight between the V6 and the V8. The driving cycle used
by the EPA has tightly defined acceleration rates and speeds. There is
not much difference in engine efficiency, so there really should not
be much difference in fuel economy. I would expect the V8 to have
better acceleration, and if you take advantage of that, you will get
worse fuel economy.

Ed

When I purchased my 2000 Explorer new, I opted for the V8.  The economy has
been pretty good, about 13-15 around town and 18-23 on highway.

I guess they discontinued that V8 (5.0), but if I get another new one I
wouldn't hesitate to get the v8.

I am thinking about buying a new Mountaineer to replace my 2003
Mountaineer. I currently have the V8 that gets...surprise
surprise....13MPG around town and 19 on the road, exactly what the new
"real world" sticker rating estimates on new Mountaineers. I noticed
that the 6 cylinder doesn't get any better mileage. Why is that? Why buy
one? Why does Ford even MAKE one if it can't offer better fuel economy
with the reduced power?