Ever tried Castrol? I heard their Castrol Syntec oil is pretty good. Some say as good as Mobil 1 full Synthetic.I have always used Mobil 1 full synthetic in all my vehicles. I also have a 2004 GMC Envoy XUV with 135000 miles on it and it still runs like new and uses no oil between changes. I also change my oil and filter every 5000 miles. Plan to do the same with my new Terrain.