Also if the hydrogen cars became the big thing, we would need to create the hydrogen through electricity, which happens to be created mainly with oil. So in reality, it wouldn't be saving that much oil to run cars on hydrogen.
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when you drive your car to work and park it.
it stays there for hours and hours.

I wonder if your car had solar power cells on it that seperated H2O into hydrogen and oxygen durring the daylight hours when your car is just sitting there.

or if your parking lot had a solar array attop it
that your car plugged into when you got to work.

if this would help to reduce the oil consumption?

3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.