Depends on where you are. There"s 2 co-ops and a truckstop around here where you can get fuel. The one co-op blends 70/30, when I gelled last winter they said I had other problems because they had blended it 70/30, and they would like to blend it heavier but their supplier wouldn't let them. And they had mixed one batch of 70/30 and dumped it in the storage tank when the forecast got cold. The other co-op runs 50/50, and the truck stop was built and is run by guys from Michigan so they just dump in the proper amount of a #1300/barrel additive.
I ran in Michigan a lot up as far as where they came from and never saw -10, doubt I saw 0, let alone -20.