The Collaborative International Dictionary
Otto engine
Otto engine \Otto engine\ An engine using the Otto cycle.
Wikipedia
Otto engine
The Otto engine was a large stationary single-cylinder internal combustion four-stroke engine designed by Nikolaus Otto. It was a low-RPM machine, and only fired every other stroke due to the Otto cycle, also designed by Otto.
Usage examples of "otto engine".
On the other hand, kerosene wouldn't work in an Otto engine, for it doesn't give off enough vapors.