Hi Chris: 08 CTS 4 15,126 miles. My CTS is a special car, used for special occasions and a few trips to Florida. PA has a annual inspection, and from 5/11/ to 5/12 I put on 1,679 miles. Last oil change by A GM Dealer was 10 months ago, Mobil 1 5W30 as required, and I have only put on abouty 1,200 miles, the oil change monitor indicates 88% remaining. Having read you exceptional post, my question, and I'm an old timer, 75, who has changed my own oil for a long time,.( Not on the CTS however.) is TIME. As an example, for years, even in some recent posts, you see 5,000 mlies or 6 months, which ever comes first. What has time, or age of the oil, have to do with its life expectancy? How can it go bad if just setting in the pan? Especialy synthetic. I'm beginning to think I shouild be changing my oil, although only 1200 miles, but almost a years life. Sure would appreciate your comments and many thanks.