@UAHMAD - They are effective only to a certain extent, they might not solve the problem but improve it. After the addition to engine was slightly quieter and smoked much less, could not really check the oil consumption because of oil leaks.
BMW S63 (newer gen 4.4L Twin Turbo) and N63 (older generation 4.4L V8 Twin Turbo) suffer with a valve stem seal issue because these motors run very very hot (110 degrees c), they become hard over time and start passing oil to the cylinder and causing the engine to smoke after a long idle (stopping at a red light or so). So in my application, I had just recently bought the car and although it was smoking after longer idles, I wanted to give a quick oil change with a flush and throw in some additives to ease things down slightly.
My car also smoked after longer idles but it was considerably improved after CeraTec and Oil Saver, and I'm replacing Oil Separators (within the valve covers) that are known to be another cause of smoking (if one of the CCV line breaks, oil separators tend to fail doing their job - separating vapor from the oil) - I plan to do a Oil Catch Can setup DIY once I'm done with valve covers.