Short answers, pulled from the story.
The diesel engine was invented by German engineer Rudolf Diesel. The first ignition took place on the 10th of August 1893 at the Maschinenfabrik Augsburg, using petrol as fuel. The main public efficiency test was conducted on the 17th of February 1897 by Moritz Schroter, confirming an effective efficiency of 26.2 percent.
A diesel engine compresses only air at ratios typically between 15:1 and 23:1, which raises the air temperature high enough to ignite diesel fuel on contact. Fuel is injected directly into this hot compressed air near the top of the piston stroke, causing spontaneous combustion without any spark ignition system.
The theoretical maximum efficiency of a diesel engine is 75 percent. In practice, passenger car diesel engines reach up to 43 percent, large truck and bus engines up to 45 percent, and large two-stroke marine diesel engines up to 55 percent. Low-speed marine engines represent the most efficient practical combustion engines ever built.
The first passenger car with a diesel engine appeared in 1929. The first mass-produced diesel passenger car was the Mercedes-Benz 260 D, manufactured from 1936, powered by the Mercedes-Benz OM 138 engine rated 45 PS.
Diesel exhaust has been classified as a Group 1 carcinogen by the International Agency for Research on Cancer. It causes lung cancer and is associated with an increased risk of bladder cancer. Particulate matter from diesel engines is also linked to heart and respiratory diseases, though exhaust gas treatment technology can remove about 90 percent of pollutants.
In 2015, the U.S. Environmental Protection Agency issued a notice of violation of the Clean Air Act to Volkswagen Group. The company had intentionally programmed turbocharged direct injection diesel engines to activate certain emissions controls only during laboratory testing, meaning real-world emissions were far higher than official results indicated.
Over 5,000 aircraft diesel engines were delivered worldwide between 2002 and 2018, particularly for light airplanes and unmanned aerial vehicles. Continental Aerospace Technologies reported it had sold over 5,000 such engines worldwide by 2018.