The cylinder walls are better if they're not completely smooth. They need to have microscopic "scratches" (for lack of a better term) into an otherwise relatively smooth finish, as these scratches hold oil to aid in sealing the piston rings to the bore, as well as lubricating the components. These scratches are made at a specific angle for the engine application/design for oil control purposes, and they're visible to the naked eye as cross-hatching of the bore. If the cylinder wall were to be smooth, it would suffer from a lack of lubrication and it would wear and score, failing prematurely.

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