I think this has to be a bug, but people are telling me that instead of buying fuel cells, they are disassembling and reassembling their machines, and getting 50 starting fuel. This is crazy! If people do this, the only people who will need fuel cells are people who go to Machine Rooms. The current expense of fuel cells is making this a worthwhile use of time, but really, using these machines is tedious enough.
10 was plenty.