system
Given the following post, respond as if you're commenting on Reddit:
human
Why does diesel fuel use compression ignition and why do diesel engines have such low RPMs?

I should clarify that I am aware of how engines work in general (intake, compression, ignition, exhaust etc). I don't need an explanation as to how an engine actually fires. I want to know what the properties of diesel are that allow it to use compression ignition instead of spark ignition. Why do the engines have such low RPMs? What is it about diesel that allows for it to create so much torque at such low speeds?
gpt
Diesels typically operate at lower RPM because the rotating assembly has to be built to withstand the high compression, which is about twice that of a gasoline engine. Steel pistons, heavier connecting rods, and a long stroke lead to more rotating mass, all of which increase the forces involved at a given RPM.