I posted earlier that I would be using Pennzoil 5w20 as the "rinse" oil for the Auto-Rx treatment in my Olds minivan. The 3.4 V6 in this van is spec'd for 5w30. For most of its life it has had Mobil 1 5w30, and prior to the Auto-Rx treatment, I ran Mobil 1 0w40 for two drain intervals. I posted a UOA for the 0w40 which was excellent. One thing about the Mobil 1: I could always count on it keeping the piston slap of the 3.4 to a bare minimum—so much so that once the engine was fully warmed up, you couldn't hear it at all. The few times that conventional oil was "accidentally" put in by the dealer, you could really hear the difference. Guess what? With the Pennzoil 5w20 this engine is as quiet as it ever was with Mobil 1. Must be all that moly. And call me crazy, but I'm extremely familiar with the sounds and feel of this engine, and it actually seems to be idling smoother with this oil. There was a particular harmonic at idle that I could always feel in the steering wheel that is completely gone now. Who knows—if this oil gives me a decent UOA when I change it out at 2000 miles I may just continue to use it. The van will only accumulate about 6000 miles a year now, so I could do two changes a year with the Pennzoil 5w20 and still be ahead cost wise compared to one change a year with Mobil 1.