What mechanism distinguishes Rudolf Diesel's engine development (1892) from Lenoir's spark ignition?

Uses the heat of extreme compression to ignite the fuel.

Rudolf Diesel’s development in 1892 introduced a fundamentally different means of initiating combustion compared to the earlier spark ignition utilized by Jean Joseph Etienne Lenoir. Diesel’s innovation focused on compression ignition, a process where the air within the cylinder is compressed so intensely that its temperature rises drastically. When fuel is subsequently injected into this superheated air, it spontaneously ignites due to the extreme heat alone, thereby eliminating the necessity of any external ignition system, such as the electric spark plugs integral to the Lenoir design.