<all> Mobil One 5W-50

[es61@prism.gatech.edu (Eric Schumacher)]

I was looking at a friend's English auto magazine yesterday and noticed an
ad for Mobil One.  The ad featured a container of 5W-50 fully synthetic
oil.  I have a few questions:

Have any of you seen this in the US?
	Would seem to be a great choice for year round use.

Is it a good/bad idea to use a synthetic motor oil with this much of a
viscosity difference?  
	I recall reading such a spread has negative connotations in
conventional oils.

Using the grades of Mobil One I have seen (15-50, 5-30, 10-30), would
15-50 be a good choice for year round use since it is synthetic?

Thanks,
Eric Schumacher
es61@prism.gatech.edu

P.S.  I saw another ad for Castrol FULLY synthetic 10w-60 in the same
magazine.