I recently purchased a 2003 9-3 (2.0T) with 170k miles. It has been well maintained and looks like it got M1 0w40 for most of it's life. I'm comfortable using M1 0w40 which is one of the few available oils that meets gm-ll-a-025, but it's not labeled as energy conserving. I'd like to maximize my mileage, but don't want to hurt longevity. I've read that Dexos1 supersedes gm-ll-a-025, which is available in a 5w30. Would this be a wise move? I'm used to my 3800s which will run on [censored] near anything, this is all new to me.