If it was not for bad luck I would have none at all!

ocdart said

I was told the same thing 40 years ago and saw the proof on the inside of a just removed valve cover from an engine that had known nothing but Pennzoil.
I immediately switched to Valvoline and have used nothing but since. Never had a problem nor have I seen sludgy valve covers on any of my engines since.

Click to expand...

I have tore down too many penz motors and when I was told the QS was the same I wasn't going to chance it. I have ran in to sludge on enigies that ran toward the normal warm side operating tempertures real often.