Good! And there are industrial patents about it since the 70's and the producers of PEA sell a lot to engine oil manfacturers to put in engine oils. Looks like it is a main proprietary (secret) ingredient in engine oils also, besides fuel system cleaner additives.
I myself like gumout all in one. I have used the gumout multi but only in fuel. It has PEA in it so its a good product. What are you looking for it to do in your oil? If you are doing regular oil changes I dont know what it will/wont do. If its a quick idle clean up before using a synthetic it might help. If you are already using a synthetic I am not sure what you will gain from it. I suppose it would do what it says but I havent dropped any in the crankcase before.