5W-30 for street use only, or 0W-40 for heavy duty/track use. I enjoy the car and live in a hot climate so I have no interest in the 30 weight.
Oils must be Dexos2 approved to retain warranty coverage, which I have right now and want to keep.
Here is a list although most of those oils have been discontinued. The only Dexos2 approved 0W-40
I can find off the shelf is either M1 ESP X3, or Supercar. I used Autozone's deals to get X3 for approx. $6/qt versus the normal $11/qt, or over $10/qt for Supercar.
Once my warranty is up, I'll move over to 5W-40 of whatever is robust and on sale.