I recently purchased a 2003 9-3 (2.0T) with 170k miles. It has been well maintained and looks like it got Mobil 1 0w40 for most of it's life. I'm comfortable using Mobil 1 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.