OK--I am a recovering Pennzoil hater who discovered bitog a few years ago. But to show myself I could be reasonable, and being a big Shell Rotella fan and with SOPUS now including Pennzoil, I have run the past two OC's with PP 5-20 and 5-30 respectively for a 2010 Mazda 3 2.0 and a 2005 Toyota Sienna with the 3.3 V6. I have owned both since new and have done all the maintenance myself. Both engines are noticably noisier with the PP, primarily valve train noise. My wife even commented on it. I have run Valv Synpower in the Sienna prior to this point and Motorcraft 5-20 syn blend in the Mazda and factory filters in both. approx 4000 mi OC intervals. Anecdotal for sure, but I will go back to Valvoline products for these two.