Go with the Mobil 1 Extended Performance (M1 EP) 0W-20. It's exceptional in that it's one of the very few fully PAO-and-AN-based oils out there, and it has GM dexos1 Gen 2, which you're asking for. It's very cheap at Walmart.
Don't go with the Mobil 1 Extended Performance High Mileage (M1 EP HM) 0W-20. It only has 5 - 10% PAO.http://msds.walmartstores.com/
Mobil 1 Annual Protection (M1 AP) 0W-20 is great, too, and also fully PAO-and-AN-based. It has even more antioxidant than the M1 EP 0W-20 for up to 20,000-mile OCIs. However, it's a lot more expensive, and you'll be fine with the M1 EP 0W-20 for up to 15,000-mile OCIs.