GM dexos oil now recommended
 

Apparently GM wants everyone to use dexos approved motor oils now...

dexos1 Brands | GM

dexos®

Green/1 is for Gasoline, Blue/2 is for Diesel

http://www.gmdexos.com/dexresource.a...ader-2-new.jpg

This provides some good background:
GM's New Engine Oil: Use It Or Else!