Blow up a balloon. Tie it off. Then add more air to it. "How?" Ahah.
...that is thermodynamics (and thus energy loss, conversion, motion, etc.) in a nutshell.
If someone can show a car that moves under its own generated power then I will show you a power source that they are hiding or hadn't considered.
How do you add air to a tied off balloon? Poke a compressed air can through the top, or bottom where it's most dense so it won't pop.
Of course, you can't poke a hole through thermodynamics though...
Yeah, you are clearly poking a hole in the system at that point.
I thought of an even better example.
Stand on a scale.
Grab yourself by the pants and lift.
Surely you are strong enough to lift enough weight to decrease the scale reading, right? No? "What if I pull harder?"
Yeah, still, no. If you couple your inputs to your outputs and do not inject anything else... there will be nothing be net loss... and even in a 100% system then there will surely be no net gain. So even in a 100% efficient system you can never do any work. All of your 'work' will be used up keeping the perpetual motion going. Suck any of it off and the system is by definition not 100% efficient anymore.