Shawn: I can only speak for the 04 and newer GP's, but the manual says that the change oil indicator will activate at 20%. In addition, there is a 600 mile grace period built into the system.
In 2006, GM came out and stated relying on the oil life monitor would not void the warranty, and they encouraged folks to do so. This statement applied to taxi/police vehicles as well.
That being said, I just did the first home oil change on my 07 at 4900 miles. The monitor was at 45%. I wanted to get the unknown dealer stuff out, and get some good Mobil 1 5w30 in there.
Anymore, 4000-5000 miles is ok as long as you change it faithfully with quality stuff. IMO, the old 3000 miles interval is not necessary and wasteful in todays computer controlled fuel injected engines.
Don
