John,
I might do that if not just to satisfy my own curiosity. If the recordings come out decent, I'll try to post them on here for others.
When I had switched to GC from GTX 5w30, even my wife asked me what I had done to the car because it seemed quieter. She didn't know I had changed the oil or anything. If my wife noticed, there must be a good difference!
There are numerous posts about Nissan VQ's liking heavier 30 weights. In Europe, up to a 50 wt is even recommended. When I used Mobil 1 5w30 (the older SuperSyn formula, about 10cst or so), the engine was very loud. GTX quieted it some, and GC is very smooth and quiet. It makes sense, because GC is a thicker 30 wt than the other two.
I'm in the rinse phase of an AutoRx run now. Based on what this filter looks like, I may or may not do another AutoRx cycle. But when I'm done with all the cleaning, GC is going back in. I have 3 OCI's stashed so far. And I've got the wife trained to pick some up anytime she's near AutoZone and they have it in stock. She actually bought me a case last time she was there because she was impressed with the quietness.
Dave