Originally Posted By: d00df00d
It's not really possible to avoid the issue of dino vs. syn entirely with xw-20 oils. Even the ones labeled as conventionals have to have some synthetic in them so they don't cook off too quickly, and a 0w-20 will need more than a 5w-20. So, if you're looking at two comparable xw-20s, the 0w-20 might be a better oil even if you don't need the extra help on a cold start.
What does this have to do with 0-weight oils, by the way? Sounds like we're talking about xw-20, not SAE 0.
Give him credit; he admitted that he's new to this, so although you're absolutely right that the question is somewhat "mis-named" I can very well see why and how it got that way.
A couple thoughts that have already been alluded to here. First, you are almost certainly getting some form of syn blend or syn when you buy either a 0w or 5w-20 oil, for the reasons df suggested. Adding to that, there are other, you might say "non advertised" benefits that would come along with that. Admittedly, it's debatable whether those benefits would be meaningful in any particular modern app, given the high quality dinos that are competing for shelf space.
The other idea I find interesting is the practical difference between 0w and 5w-20 oils (same being true for the 30s and 40s too). Studying the numbers (and admitting that I'm not an engineer), I really wonder how many situations exist in which there's really a meaningful benefit with the 0w compared to the 5w... If it ever becomes a factor where I live (Florida), you guys up north will probably have had a glacier push your house over. And even up North, how often do you really see temps cold enough to bring the differences into play?