The subduction zones obviously take cubic miles of ocean floor deep into the earth. That ocean floor is composed of... carbonates from eons of marine life fallen to the bottom.
Take that DEEP into high temperature and pressure and you get OIL ! ! !!
So it's renewable, limitless, and self-cleaning. The CO2 is recycled by organisms everywhere.
QED
And all that heat fromt he earth’s core comes for the decay of elements like Thorium, so Oil is powered by Thorium!!!
If we could harness that power somehow, somehow.....