...I am driving the same roads, and the mileage I compute from fillup to fillup. There is less than 1 mpg difference between the two.

Nevertheless, I will say that there are a few variables in play, including MUCH lighter wheels on the 4.2 (those Volks are very light). However, I think the V8 makes up for the thrist in its ability to cruise at lower RPMs, plus the fact that there is no turbo lag (instant power), so there is less temptation to slam the pedal down to make passes.

I also think that I am MORE diligent about keeping optimum air pressure in the tires in the 4.2, since I am running the 18" wheels. Less sidewall on these wheels, so I probably check a bit more often than I did in the 2.7T. I think in the V6 with the 17s, I checked at least once a month. In the V8 with the 18s, probably every other week, but never more than 3 weeks between checking air pressure.

Just my two cents...your mileage may vary...