Something like burner fuel bonuses, but based on the temperature the machines achieve.

Love the idea. In version 17 this would have required creating an array of entities and scripting them to be swapped out at different temperatures (introduces a huge interface for error). I'll take another look at it when I'm ready to do a version 18 overhaul. I appreciate all your feedback, and I will get to it at some point -- we're crazy busy at work right now.

Well, burner fuel bonus already does something VERY similiar. So it's probably doable. Since it WAS done already.

The problem is attaching the temperature to the mechanism. There was no engine-supported way to do that, so it involved a script that monitors temperature. And then to actually change the efficiency... so the entity has an "energy_source" object, and if memory serves, the burner type of this object has a bonus attribute that doesn't exist for the heat type, so the potential solution was to actually create each stage of increased efficiency and have a script swap them out. Pretty convoluted. I'll take another look at what the options are, though.

I also explored adding a neighbor bonus, and there was some reason that didn't work...