A neighbor who runs a lawn care service installed these in a couple of his vehicles, convinced it would save him a lot of fuel costs. Like others on here, it was pretty obvious to me that the small amount of hydrogen generated was not going to offset much gasoline burning. Something that didn't make any sense to me at the time....he said they recommend putting aluminum foil over the oxygen
sensor. So, perhaps to be able to humor him or explain how he was likely to be disappointed, I started searching the internet. No, really, I was just curious. I found all the adds, the long history of these devices, descriptions of lawsuits, etc. I ended up on Wikipedia, which if I recall correctly, is where it all started to make sense. These things seem to help engines run with leaner gasoline air mixtures at idle and low speeds, like city driving. In cars so equipped, they cover the oxygen
sensor with foil to make it run hotter, which apparently results in the injection computer calling for a leaner mixture. The hydrogen/oxygen mixture that comes from the jar from the electrolysis process (driven by the 12V car system) aides in combustion of the leaner gasoline air mixture, thus saving some gasoline. How much, I have no idea. The Wikipedia authors were cautiously supportive of the idea, saying the hydrogen/oxygen mixture results in acceptable exhaust products, doesn't hurt anything, and may have some benefit. So, I'm looking for my neighbor to see how he's doing by now.