A minor change in axle ratio won't cause a major change in fuel economy. I think Gerry has already done the MPG calculations over time and found exactly that. My estimate would be ~10% difference, maybe.

FWIW, 2.88 vs 3.06 is splitting hairs... like, 1-2 tenths of a second 0-60 (or quarter mile) and likely under 1mpg difference in fuel economy.

The lower gearing makes it snappier around town, which is nice if the car is primarily city-driven.