My kneejerk reaction is that it doesn't seem wise to run your previous breathing gas through an ICE but surely its not as boneheaded as it seems at first glance?

I've wondered how heavy construction equipment would work. Bulldozers trailing thick power cables seems... problematic. Yes, I'm aware of huge draglines connected to power sources with cables, but they aren't very mobile and you don't need to worry about other equipment cutting the line. Don't think batteries would do, either. So, ICE with compressed oxygen?

I would think the weight of batteries would be helpful in the case of bulldozers, especially given the low g.

Well there's likely to be surplus rocket fuel available, either RP-1 (kerosene), methane, or liquid hydrogen, and LOX, so burning some in an (non-rocket) internal combustion engine is not so crazy. Fuel cells would be more efficient though.