The 19th-century engineer was Rudolf Diesel.
Rudolf Diesel, a German engineer born in Paris in 1858, developed the compression-ignition engine that became known as the diesel engine. Unlike a typical gasoline engine, it does not require a spark plug to ignite the fuel. Instead, air is compressed until it becomes extremely hot, and fuel injected into that hot air ignites.
Diesel pursued the idea because he wanted an engine that could convert more of its fuel’s energy into useful work than contemporary steam engines. He patented his engine concept in 1892 and built experimental machines during the 1890s. A successful early engine demonstrated the practicality of compression ignition and led to commercial development.
Diesel engines are often associated with diesel fuel, but Diesel’s original design could operate on several fuels, including vegetable oil. At the 1900 Paris Exposition, one of his engines reportedly ran on peanut oil. The key identifying feature is the ignition method: compression rather than an externally supplied spark.