Just for reference, my last car was a 2002 Grand Am GT. I used GM's "Oil life monitor" system, which had me changing the oil well beyond 5,000km intervals. If any engine would have been hurt by longer periods between oil changes, this iron block, aluminum head, pushrod V6 that was wound out to redline a lot during its life would have been it. I always changed the oil when the "Change oil" light came on, never before. When I got rid of it, it had around 215,000km. The engine ran perfect with no unusual sounds. It didn't burn oil, I didn't have to add oil between changes, and it ran clean. It passed drive clean last October with excellent numbers. I got rid of it because it had other issues that were not related to the engine. I believe the engine would have been the last thing to fail.