I am chaning oil at 500 miles. Here is why. Onwers Manual says vary engine rpm and not exceed 4,000 rpm for first 500 miles. Then start to gradually increase rpm. OM also says no towing for frist 500 miles. Then it says change oil before heavy towing. So if you are planning to tow, GM is advising to change the oil before you tow, and GM says you can start towing at 500 miles. My opinion is GM is recognizing that it is better to have clean oil before you start loading the engine. I plan to start loading the engine as soon as I hit 500 miles.