I have noticed a lot of new cars/trucks that have shutters and/or flaps that close off parts of the grill openings to achieve better aerodynamics and ultimately, mpg. Most new cars do the majority of the cooling airflow from the lower openings. I was wondering how the S-Type would do with the front upper oval grill closed off?

 

You will kill your "cold air intake" if you close the top grille. The stock STR intake pulls the "cold air" in from an opening right behind the grille.

Other than that the lower grill will get air into the radiator etc, but not as much as you get with both grilles functioning, IMO I think you would run a bit hotter especially on a nice warm sunny day!