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Comment by userbinator | original | Internal Combustion Engine (2021)
[−]userbinator · 2026-07-02 Thu 00:37 UTC · link
While they look perfectly round, piston skirts are actually slightly oval.

...something which has been the case for at least 80 years:

https://news.ycombinator.com/item?id=15397926 (the article in that link has now moved to https://www.web.imperialclub.info/Repair/Lit/Master/003/inde... )