I'm looking for input to help make a decision. I favor Pennzoil Ultra or Mobil 1 Extended Performance for my 06 Impala SS. My driving consists of short-trips between 9-15 miles one way five times a week, and then various other driving environments including highway. The OCI varies, but generally I follow the OLM. Are these Oils so close it doesn't matter? Or, is there clear proof one is superior to the other. I have viewed many UOA's and that, to me, seems inconclusive. I do know there is a veritable thousand years of lubrication experience on these forums, so there many be something to lean one way or the other. Any help would be appreciated.