Do you actually have your car sitting out all night when it's really cold?
Do you actually see temperatures of -40C, which equals -40F?
If not, you are worried about nothing.
GC meets the specs for a 0W-30 oil.
It is thinner than any 5W-XX at really low temperatures.
It could not otherwise be a 0W.
Now, getting practical, both of my Accords have run GC during the winter, and both were fine down to about -10F, the coldest they saw on GC.
OTOH, the coldest I've ever stated a car that had spent the night outdoors was with our old '76 Civic, back in the early 'eighties.
The temerature was My point is that if you want to use GC, go for it.
I can't see it hurting your engine.
A more pertinent question might be why you want to use GC.