Nikolaus Otto invented the first practical four-stroke internal-combustion engine, patented in 1876. The cycle became known as the Otto cycle and remains the operating principle of most traditional petrol engines.
The four strokes are intake, compression, power, and exhaust. A piston draws in the fuel-air mixture, compresses it, receives ignition that drives it downward, and then expels the exhaust gases. Otto’s engine was developed with Eugen Langen and engineers at the Deutz gas-engine company.
Earlier inventors had built internal-combustion engines, including Étienne Lenoir, and Alphonse Beau de Rochas had described the four-stroke principle before Otto’s practical engine. Otto’s achievement was turning the concept into a reliable, commercially useful machine.
The engine initially ran on gas rather than petrol. Later designers adapted the cycle for gasoline-powered vehicles. Gottlieb Daimler and Wilhelm Maybach used related principles in high-speed engines, while Rudolf Diesel developed a different compression-ignition cycle. Thus, “Otto engine” specifically refers to spark-ignition engines using this cycle.