winter oils

[feelstranger]

Hello folks.
Things have been so quiet here.
Anyway, I wonder what people are running in cold weather areas like the NE?  
I an considering switching to synthetic for the winter.  The car has never had synthetic in it as far as I know but that is not a problem anymore, correct?
By the Book, 10W-30 is not for below about 5F and 5-30 is not for above about 15F.  That's a tough overlap when temps in the morning may be -20F one week and day time highs in the 30's the next...
Nat