eh, myself personally, i'd go with 3.90s. great street and track gear. as far as mpg change, it would depend if u do alot of freeway or in town driving. in town, u really won't see a change with 3.90s, freeway you will maybe see 2-3MPG change. with the 4.10s, ull see a slight increase from the 3.90s, but not by much.