I am a new owner of a 2005 Chevy Trailblazer w/ 45,000 miles. I am almost at the end of the RX cleaning. After the rinse cycle, I am going to a full synthetic. I have not found much history of oil on the I6 aluminum engine. I have an extended warranty on the vehicle and want to stay with an "approved" oil for that duration. My thoughts as of now are between M1(which one), PP, or Havoline. I am not quantifying cost/benefit. Any help appreciated.