[Rimrock]

The inner of a cylinder tube is in real life not polished, for some good reason. There are some traces, crossings, from more or less course honing tools, up to like 300-400. This apply also to engine cylinders. These traces are there for getting a thin layer of oil film on the walls to lubricate the gasket / piston ring contact surface. If fully polished no oil can stay there. In the scale world it's no big deal, and one can not get it fully polished anyway so a bit oil fill always manage to stick there. Do as you like, what makes you sleep better in the night, polish or just leave as is. I sometimes use a tool called 'Flexhone' and run it through the cylinders a couple of times, other times glue a 600-800 grit paper to a rod and pull through. Most cylinders that are ready made in the scale world have not been threated. But again, no big deal as one not operate 8 hours a day)