gas engine

noun2

1. •
   An internal combustion engine that runs on a fuel gas (a gaseous fuel) such as natural gas or producer gas; especially, a reciprocating one, typically a large stationary engine in power plant or industrial use.

   • The shop was driven by a hiccoughy old gas engine which sometimes packed up, to the great delight of all the juveniles. — 1944
2. •
   (US, Canada) An internal combustion engine that runs on gasoline; especially, a reciprocating one.