Going full synthetic can never hurt anything. An oil analysis is also in order if you want the EXACT answer.
European makes seem extra obsesses with long change intervals so have additive packages to account for this. You might look into one that meets spec for VW/Audi, Mercedes Benz, etc. but BE SURE it still meets Dexos, at least while the engine is under warranty.
It is my belief that the European standards for synthetic oils are far better than those in the US but you want to use something with the GM stamp of approval on it during the warranty term.