How often should my oil be changed?

According to the normal maintenance schedule it is recommended to be changed at 7,500 miles and according to the severe (driving around town with lots of starting and stopping, mountain driving, dusty conditions, things of that nature) it is recommended at 3,000 miles for your G6. Also depending on the engine you have some are more susceptible to sludge than others, so changing it sooner rather than later will not hurt anything.