I have used Auto-RX a couple times in the motor of this 200,000 mile 89 Ford Taurus SHO  once or twice about 40,000 miles ago and once a few thousand miles ago followed by a rinse phase and then another oil change with some inexpensive Chevron oil that was on sale. I only kept that Chevron oil in there for a few hundred miles and then pulled the oil pan at 200,000 miles so I could replace the rod bearings for preventative maintenance.  I didn't want dirty oil dripping on my face. A little wasteful, but it's much nicer working with parts that are coated with clean rather than dirty used oil. Very clean inside!  It was obvious which places got a steady flow of oil because they were absolutely clean.  Everything else had at most a light caramel colored varnish which wiped off fairly easily for the most part.  Several years ago you told me about the easy to wipe off varnish for parts not constantly exposed to oil flow. There were a few small nuggets of carbon in the oil pan which were too small to pass through the oil pickup tube screen.  There was no sludge anywhere.  My rod bearings were in pretty good shape too and of course they had no varnish on the bearing surfaces.  I have been a believer in Auto-RX because I have been treated to a smoother, quieter motor following its use.  I wasn't disappointed when I took the oil pan, baffle plate, and support girdle off and saw what could have been a picture of a well kept, very low mileage motor.