[Shortie771]

I personally just don't understand SUVs unless you plan on going off road. The 2017 Acadia has 1 cubic ft more cargo space than my wife's 2012 Civic, both have the same number of seats and plenty of leg room... I just don't get the appeal.

Well enough of that rant... To answer your question, yes. A grill block will help your gas mileage, by allowing your car to get to normal operating temps faster and also improve aerodynamics on the highway. A smooth underbelly will help a lot as well, though those are starting to come on many factory cars now in order to help meet EPA standards. Check out what it looks like under there first, if it's clunky and rough (like the pic Freebeard posted) then a belly pan will definitely help.