Hello MKTSC
I currently use Mobil One Syn 5w30 in my car; listed in sig. Amsoil is the original maker of synthetic oil, and specifies when following correct instructions, you can change your oil at intervals up to 30,000 miles. I have also heard it to be a good oil from a few sources. Mobil One was the second maker and is currently widely supported as the best.. I believe they started in the 80s.
As for viscosity, I have heard significant evidence suggesting higher weight oils should be used in modified SC engines, due to increased loads put on internal engine parts and oil viscosity. However in a stock SC engine, 5w30 should be satisfactory for wear so long as oil is changed 3000 mi. A significant portion of engine wear on a stock daily driver occurs during startup, this is why 5w is recommended. As previously mentioned, synthetic is prefered on these cars due to greater demands placed on oil viscosity from the supercharged engine load. Remember its still a 6 cyl, even though it has the output of most 8s.