A petrol engine (gasoline engine in American English) is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as E10 and E85).
Most petrol engines use spark ignition, unlike diesel engines which typically use compression ignition. Another key difference to diesel engines is that petrol engines typically have a lower compression ratio.
Wankel engines are classified by the number of rotors used.
Petrol engines use spark ignition and high voltage current for the spark may be provided by a magneto or an ignition coil. In modern car engines the ignition timing is managed by an electronic Engine Control Unit.
Power output and efficiency
The first practical petrol engine was built in 1876 in Germany by Nicolaus August Otto, although there had been earlier attempts by Étienne Lenoir in 1860,: p15 Siegfried Marcus in 1864: p79 and George Brayton in 1876.: pp413–414 
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- CA 6479 "Gas Motor Engine"
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