The question is not if Supertech or Kirkland are suitable oils. The question is are they suitable for your application/conditions.People on here like to refer to Kirkland oil as a lessor or lower tier oil. There is a post on here where the same driver in the same vehicle ran Mobil 1 5-30 for 5k miles then had the oil analyzed. Then he ran Kirkland 5-30 for 5k and analyzed it. He posted both reports. The different categories reported almost identical. If you hid the names, you couldn't tell them apart and might think it was the same oil. Now that doesn't tell us about sludge but it says a lot for Kirkland oil.
Maybe, yes. Maybe, no. Maybe, maybe.