At some point we’re just getting bogged down in semantics. Someone invented the internal combustion engine, and the earliest versions ran on gaseous fuels. Somebody else “invented” versions that than on liquid fuels. Engines that ran on petrol (gas) and diesel were “invented” by separate people. Engines based on turbine, reciprocating pistons, and rotary mechanisms were all “invented” by separate people.

The degree to which you consider any of those independent “inventions” versus simply modifying and improving existing inventions is essentially arbitrary.