I started not to even join in on this thread because it normally turn to war but it's been friendly so far. Lil Foot reminded me of a do it yourself test that anyone can do at home for very little money.
The freezer test:
I compaired Rotella 15w40 to Amsoil 15w40. One quart of each in the freezer overnight and the next day do a pour test. It's easy to do and you can see for yourself which oil has better cold weather performance.
Curious about a certain brand, spend a few bucks and see for yourself.