BLKBRD... So you don't trust Wikipedia? Me neither, it was just an example of an article that explained that "W" means "Winter". How about Castrol? Would you believe them? They make motor oil, read what they say:
Motor oil viscosity - Castrol Motor Oil
W means Winter. To write "30w" in reference to "30 weight" would be confusing terminology, "SAE 30" or "30 weight" or "30wt" is clearer, and that is the terminology the SAE and thus I, use. In your quote above, 0w does indeed mean 0winter oil, ("The "W" refers to low-temperature performance," not weight), but as you posted there is no 30winter grade.
I don't mean to sound like a jerk (like my avatar, "The Jerk"), or know-it-all, and I apologize if I come across that way. I admit I was tired and a bit grumpy when I wrote that other post, but I can lose my patience over motor oil - It's one of the few automotive subjects that I have a passionate opinion on..... Because I do my homework. How many people worry about the sulfated ash content of their oil, for example? I research which brands have the lowest percentage. (Shell Rotella, if you were curious). I read about the chemistry of oil because I like to know what oil companies have added to their base stock and why. I find such things fascinating.
Everyone if free to use whatever oil they like, but there are too many who use the "wrong" oil (meaning not what the equipment manufacturer's engineers instruct you to use) because "I always use this oil" or "My Dodge truck takes 15w-40 so it must be right for my deuce". Follow the equipment manuals (aka TMs) and you can't go wrong.
Jon