I'm currently working on a Fantasy story set in 2055. By then, people will probably be moving away from gasoline, so for realism's sake I thought it would be wise to come up with an alternate power source for automobiles. It's not particularly important for my plot, but so far, I've been using cars that run on water. It's sort of a closed-loop: put water in the "gas" tank, electolysis converts it to hydrogen, which is then combusted in an engine, producing mechanical power, electricity, and water as a by-product. Only occasionally would the owner of the vehicle have to add anything, and that's only because the system isn't completely in balance. it's never explained in that muhc detail in the story, readers only know cars run are fueled by water and contain explosive hydrogen somewhere inside. Like I said, it's not super-important to the plot and I'm open to other ideas. I'm just wondering if this sounds feasible or will readers get hung up on it? I can only think of two small instances where it becomes relevant to the plot. (1) One of my characters, who is a 1,000 year old vampire, drives a gasoline car, which is basically considered an antique by most people's standards. (2) I wrote a fight sequence where one of my magic-users makes a sword of ice using water from a car's gas tank. Both of these are only minor things and can easily be edited out if need be. Note: I considered placing this in "Research" but because I'm not looking for specific facts, just people's opinions on the subject, I figured this was the best place to put it.