I’m obviously not as comfortable in my box as you are in your ignorance.
Let me explain to you. Someone who lives in this sort of imaginary box doesn't explore anything beyond his comfort zone even though his comfort zone is far short of some real possibilities. I meet engineers like you all the time. But that's okay I forgive you.
For your information my little boxy friend, there is already a design for a self sufficient automobile. As you said, motion is indeed work and requires energy, but it is also a resource for energy at the same time. Supplemented with solar skin and the like a vehicle will never need to fuel up or plug in. Ever. Weight will be a factor so steel will be out of the question.
The negative about this is economic. Our economic system isn't ready for technology like that. We still rely on the 100 year old plus design of the internal combustion engine because it employees more people not because we can't get design anything better. You see, our economic machine can't get out of its own way.
At the very least, even Carroll Shelby and John Luft are saying the current design of the internal combustion engine is obsolete. Check out the OX2 design. They haven't gone as far as what I am saying, but they have certainly left the box.