I DO know that the "special" ingredient in ZMax has been tested since the 1940's in aircraft. That "special" ingredient has FAA approval for use in piston aircraft engines as a lubricant. FWIW, the FAA doesn't allow just any additives to be approved....
Does it work in cars? Who knows. But it has been used in aircraft for many years now and is approved for use by a government body. Food for thought...