Well, my Volvo got a golden shower this morning - 6 quarts of GC gold. I am amazed already - the pain in my right knee is gone, and my vision has improved to the point that I no longer need to wear my glasses. This stuff is amazing!
Seriously though, I do plan on monitoring the oil to see how well it works. I reset the Avg MPG on the trip computer to see if there is a change. However, I think we are now into the winter blend for gasoline, so any MPG tests are probably void. I will also have the oil analyzed in the spring. Not sure there much else I can do. While I swear my engine is running smoother with GC, I get the same sensation after a car wash. My cars always seem to run better when clean, and when the sun is shining, so I don't put any stock in the buttocks sensor.
Let the fun begin!