"It's been known for a long time (~200 years) that electric motors are more efficient. "
"Exactly. That's why diesel-electric locomotives won out over diesel."
You've got to be a bit careful in the assumptions here.
diesel electric and hybrid cars both still use combustion engines to turn fossil fuel energy into motive power in the overall system.
What the hybrid and diesel-electric change vs traditional combustion is then converting the motive power into electricy and then driving a generator.
This has two effects:
- electric motors have ability to be efficient across much wider speed ranges, so you save yourself from gearing and transmission loss (think 5 speed transmission vs electric motor drive).
- because the combustion engine doesnt have to be driving the car directly, it can be run in more controlled RPM and troque for max efficiency.
But you still have the internal combustion in the chain of power, which is at best 40%-45% efficient.
In any event, you still need to generate power via electricity, which is currently in the form of natural gas etc. If the entire nation moves to electric or electric-hybrid and cut oil consumption dramatically, we'll need to convert to nuclear energy.