Auto-Rx won't remove the brown stain in the pores of the cast aluminum parts. It will liquify varnish, carbon, and sludge for removal either in the filter or the oil drain. It worked very well in my '96 850T...the turbo boost gauge seem to climb faster now when I mash the pedal. Many folks report more junk removed during the "rinse" portion of the cleaning process which is just running regular, non-synthetic oil. Heavily sludged engines or engines with rings stuck in the grooves with carbon will benefit from the two-cleaning routine. I've used it in two engines and one transmission so far. I'm satisfied.
Two interesting official documents:---the patent office's seach function is down as I type, so put in Auto-Rx's patent number, 6,544,349, into
http://www.uspto.gov/patft/index.html and read what it says. Also note the Material Safety Data Sheet data on the Auto-Rx.com site...nothing hazardous or toxic.
Ken