The semi-diesel in M18 used an externally heated bulb to ignite fuel at a lower compression ratio than a true diesel. Once running, combustion supplied enough heat for the engine to continue without the starting torch. Its ability to use kerosene, heavy bunker oil, and fuels between them offered valuable logistical flexibility during wartime. The tradeoff was a finicky mechanism that demanded careful maintenance and did not tolerate salt water well.
Notable Point · 23:38-25:15
M18's adaptable but temperamental hot-bulb engine
M18's semi-diesel hot-bulb engine could burn several heavy fuels, a wartime advantage balanced by difficult maintenance and salt-water sensitivity.