Google is your friend here, but I will post a link below. Read the part from the Ford Engineer.
I started life with a scholarship from Mercedes Benz and after university worked for them as a design/testing engineer for several years. When the oil additive folks organized a demo and they heard I was going to turn up, the demo was always cancelled. Some of them would run the 4 ball oil test and once they throw their magic lube additive onto the gizmo, it would show superb performance compared to normal oil. My favorite was to get a mechanic go fetch some high pressure diesel oil and outperform their additive. Then explain why neither is necessary. In short, you will end up doing a lot more damage than good. As said before, it compares to drug addiction. You may find a nice power bump on a dyno after adding the additive and then have to redo the motor about 15,000 miles later.
Car Bibles : The Engine Oil Bible : Additives