What about hydrogen fuel?
I have an issue of Scientific American which promises pie-in-the-sky for this. Is it too good to be true?

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"I am happy to report that once again the universe is doing just great, thank you, purring with perfection, ever-changing same as always. Light is still cruising along at 186,000 miles per second, and the expanding universe shows no signs of contracting. At this rate, it won't be long before they'll have to let the photon belt out another notch."
Swami Beyondananda's 2007 State of the Universe address