I'm debating which weight to put into the truck for the winter. Correct me if I'm wrong on this, but wouldn't both 5w30 and 10w30 have the properties of a 30 weight oil in the winter? I have always run 10w30 in the summer and 5w30 in the winter...but now that I think about it they both have the same viscosity in cold temps, right?? So to this end, there's really no reason to use anything but the 10w30. I'm starting to confuse myself...any help you guys can offer would be appreciated.