Most, if not all fuel additives, oil additives and all other proclaimed "miracle-in-a-bottle" can be qualified as being some form of placebo.
The Federal Trade Commission in the US and Consumer Reports have run thousands of very serious laboratory and on-the-road tests on hundred of those magic potions and very few if any have been proven to deliver any real/measurable benefits. Some have been proven to be the cause of serious engine problems (Slick50 is one)
Most if not all serious engine manufacturers clearly advise not to add any additives to their engine.
The additive industry has built a multi-billion $$$ market based on clever advertising/marketing campaigns but have never been able to convince any serious car manufacturer to endorse their products. That says a lot. Many/all additive manufacturers claim their products will Increase performance, increased mpg, decrease wear in addition to other benefits, which is really the goal all engine manufacturers are running after. If these goals were achievable by the simple addition of a secret miracle liquid in a plastic bottle, I am positive engine manufacturers would be the first to recommend/endorse these products.
Save you hard-earned cash for a nice cold beer.
JackD