There is probably little, if any, viscosity improvers (VI) in the 0W-40 Mobil 1. This is one of the advantages that synthetic motor oil has over petroleum based oil. Having said that, I agree with Larry -- why would someone who lives in FL need this?
I used 0W-30 Mobil 1 last winter in my wife's car and, although it worked well, was probably overkill even here in Minnesota. I think I'll use the 5W-30 version this winter instead.
...and keep changing the oil and filter regularly no matter what oil you use!