Smog Comes From Tiny Crevaces

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990019483.pdf

I was researching hypereutectic pistons and this came up. I found it fascinating.
A few interesting facts.
Smog is primarily unburnt fuel.
Unburned fuel comes almost entirely from the little crevice between the piston and cylinder wall above the top ring, around the spark plug threads and head gasket gap.
The middle section gets technical and boring. The conclusion gets interesting again.
It's over 20 years old so I imagine the new alloy is in use.