Depends on the brand, so one way to get the 0 rating is to add pao, and one way would be to add vii's, so stay in grade specs hint that considerable amount of pao is used in some 0 winter rated oils, especially various m1 offerings. So bottom line, some 0w30's only carry an upside, because most of the 5 winter rated oils don't bother with stay in grade specing, or when they do it is easy to stay in grade because of the swing between winter rating and weight. In cold places 0w30 will flow much better than 5w30 at start up, but flow the same at operating temp, look up cSt's of both oils you will see.
Look at chart, pao second line, that base oil doesn't need gimmicks in the base oil to flow in the cold, and has better heat properties as well. So less vii's, less pour point depressants needed because they naturally flow in colder temps. Only downside is cost.
You see mineral oils can operate at low temp, but another fact is these oils will flow thinner at cold temps, which doesnt mean it flows thin, even when they are cold they are thick, just less thick then mineral.
