A piston is anything but a slug. It's asked to withstand the cylinder pressures generated by 200,000,000 power strokes (in its 100,000-mile lifetime), slide in bores with a minimal amount of ...

It's amazing that an object as simple as a piston can withstand the rigors of combustion for hundreds of thousands of miles without failing. There's a lot more to a piston than meets the eye, matey.