I participate in a forum that is dedicated to running a car on water the way Stan Meyer’s claims he did. He was an interesting person. He spent many years experimenting, testing, and building prototypes. He has many patents that talk about different aspects of his process. He has videos of an engine supposedly running using his process. He has given seminars which sort of describe it. He was supposedly murdered by people who did not want his invention to be marketed. He is considered by some to be a con artist because he took investors money but never produced a commercial product.
Since his death many have pored through his notes and patents to try and duplicate what he did, but as yet no one has succeeded. Although some think that they are getting close. He was supposedly a somewhat paranoid individual and was worried that his invention might be stolen, thus like Nostradamus, he wrote in a rather cryptic manner which no one has been quite able to figure out. Which is why some consider that he was just scamming people to get them to invest in his process.
So was he a con artist covering his butt or was he a paranoid individual trying to hide his inventions? I would like to assume the latter, but for me that is still an open question. In either case he managed to effectively hide exactly how and what he did.
On the plus side many have been using a version of his process to make small amounts of HHO gas that is then added to air intake of a regular gas engine, this has been reported to give a significant improvement in mileage. Some claiming as much as 50%!