My father in law is the manager of the fuels and lubrications department at GM. I will see if I can get any insider info from him. He has confirmed that any SFI rated oil should work fine under any "normal" driving conditions and in stress tests done with a corvette, it has performed as well as any synthetic made even under extreme driving conditions. The extreme conditions only shorten the length of the oils life.
He also made the point that the average driver who is not real aggresive should expect to get 6-7000 miles on standard SFI approved oil. 3000 miles would only be required for people who drive like most of us probably do, hard. That being said, i still change mine every 3000 miles for piece of mind and habit, not out of necessity.
