By Lake Speed Jr. and Keith Jones
No experienced engine builder would intentionally bolt a cylinder head to a block without installing a gasket between the block and cylinder head.
Why? Because the gasket seals the block deck surface to the cylinder head surface. As we all know, a piece of metal that looks smooth is actually rougher and wavier than it appears. That microscopic surface roughness and waviness create leak paths, especially under high cylinder pressures.
Gaskets are used to fill the voids and contain those high pressures. That’s why really high horsepower engines O-ring the blocks and heads!
So, what does this have to do with motor oil? Well, those same microscopic peaks and valleys also exist on the cylinder walls, piston rings and piston ring grooves. What fills in those valleys and covers those peaks? Motor oil, which acts like a gasket to seal those components together.