Originally posted by fastcougar:
Read this: http://bestsyntheticoil.com/dealers/amsoil/5w20-cafe.shtml



That's purely Amsoil marketing, and out of date too. They're now carrying a 5w20 and wow, look at that, it works great.

http://www.amsoil.com/storefront/xlm.aspx

Anyhow, if you're using mobil 1, their 5w20 is on the thick side of a 20 weight and their 5w30 is on the thin side of a 30. So, there's actually pretty little difference between the two.

More info (pull up a chair):

http://members.rennlist.com/oil/Motor%20Oil%20101.htm