Man who invented Gas Pill?

I recall reading something when very young, about a man who invented a "gasoline pill". How it work was he simply placed the pill, in a water-filled gas tank and the engine ran flawlessly. From what I can remember, he had demo'd his pill on a Lawnmower, in the early 1900's (not sure if there were gas lawnmowers then, but I could be mistaken with the date, I was young) CIA or FBI agents (not sure of this either) showed up to look at his invention. Soon after, the man then simply "dissappeared "(this I'm sure of). Anyone else read this? I was telling this story to some buddies and they all think I'm nuts. Tks.