Yea flex-fuel and multifuel wold be cool (are those different things? From your description multifuel sounds more accepting than how I understand flex-fuel to operate, which runs on arbitrary combinations of gasoline and ethanol)
Something technical that’s been holding back adding more fuels is that the game engine would only accept a limited number of fuel types, and we were already at the limit (enums 're baaad mmkkkaaaayy…?), I have a pending fix that adresses that and allows an arbitrary number of fuel types. With that out of the way, it’s a matter of adding more engine types, and probably cleaning up how different engine types are handled (right now adding a new fuel type would require updating like um… checks 17 different places in the code). I guess each fuel type would need its own tank, because a gasoline tank would only accept straight gasoline, a flex-fuel would accept gasoline, ethanol, disel, and possibly kerosene (not sure about the last one), whereas a multifuel may well accept any flammable liquid, and a potential ethanol-only engine would want pure ethanol.
For a steam engine, I think we’d want to just have a boiler unit that consumes water and whatever fuel it uses and produces power. That boils down (ha) to whether it’s desireable to have multiple fuel sources for the boiler, or multiple boilers or whatever, in which case seperating out the turbine or pistons might be called for. Probably not though.
None of this is terribly difficult, it’s mostly held up by the way engines are handled, they don’t have stats, the stats are scattered all over the code that interacts with them.
