Maybe you can add Things like Methane/octane each with their own combustion temperature plus the ability to mix them, And give them boiling points to match real life What i mean is hydrocarbons from Methane, Ethane, Propane , Butane, Pentane, Hexane, Heptane, and Octane.
Multiple, Like Methane would be Mthn, Ethane would be Ethn propane would be Prpn and Butane would be Butn and pentane would be pent and so on I Forgot, When they burn it would create Wtrv/CO2
Actually I realized maybe making GAS a varying element would be cool because the ctype can change what it acts like same with OIL