I thought I would share the oil analysis I recently received from Blackstone labs.
2006 Impreza TR, 80.000 PLUS miles at the time sample taken. Daily driver, no mods. Started from second oil change after the car birth using only Mobil 1 10W30 either 5W30 depending on the time of the year.
Replace oil every 5K, +/- few hundred miles, not principal IMO to be exact. Seems Mobil 1 doesn't do too bad.
Here the results: