My car idles around 600 RPM which is equal to about 10 cycles per second and redlines at around 6,000 RPM which is 100 cycles per second. This just seems like a more friendly scale to use. I am curious why we use RPM instead of Hertz to measure engine speeds.
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Its a convention that emerged during the steam era. Steam engines turned much more slowly than modern internal combustion engines.
Engineers held a watch and counted shaft rotations to determine engine speed; a minute was a convenient period of time for this purpose. Before accurate speed gauges were common, counting turns was the only real way to detect subtle speed differences (e.g. 60 RPM vs 61 RPM).
Even as engine design speeds increased dramatically, no compelling reasons emerged that led engineers to measure engine speeds by units other than that with which they were already familiar.
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