There are a few items on the web about these additives and I generally concur with the "snake oil" theory. There ain't no substitute for good clean oil.
1946, slightly off topic but adding a bit of 2-stroke oil to the fuel is another method of improving your upper cylinder lubrication. This cunning tip was passed on to me by an Auster owner of long standing who has recently emigrated to Gippsland. He swears that it has eliminated any sticky valves on the succession of Gipsy and Cirrus powered AUsters he has owned over the years.