just to clarify, the standard definition of 'combustion engine' includes steam engines https://en.wikipedia.org/wiki/Combustion_engine, while it's mcdonald's personal definition of it that doesn't

as for the pedantry, though, guilty as charged

there is a shorter term for 'internal combustion engine' that doesn't have a conflicting standard definition; you could call them 'explosion engines', which is what we call them in spanish (because 'motor de combustión interna' is even longer). sometimes this term is limited to otto-cycle engines (as in https://es.wikipedia.org/wiki/Motor_de_explosi%C3%B3n) but logically should include diesel engines as well

in addition to lacking a conflicting standard definition, 'explosion engines' has the advantage that, like 'dynamic programming', it makes the subject sound more exciting