Is there any real purpose for those wind deflectors on the front of all the Suburbans, tahoe's and Yukons? I still see so many with cracked windshields , with or without the deflector.

About the rear wing that i see attached above the rear hatch, does this really keep th rear window cleaner and save fuel?? i have been told both but then i was told by one guy he thinks it created more drag and turbulence at the back.. so any input is great on these subjects THANKS!