Hmm, does this mean that, for example, a ship with an engine block made of many small engines will be cheaper to maintain than a single big engine, in general, given that a maintenance failure hitting the engine's DAC will cost much less?
Purely looking at MSPs expended, yes, but such an engine block will also burn considerably more fuel and be far more expensive in overall terms (and thus also while in orbit of Maintenance Facilities). . . and if the small engines are small enough to drop below 1 HTK, then they will all blow up together very quickly.
Comparisons are posted in the Engineering and Maintenance thread.
Do smaller engines cost more for their size? I thought the increase of cost was based on EP, so all you lose is fuel efficiency.
Engine cost is directly proportional to size.
The maintenance savings occurs because you aren't increasing the chance that the engines will be hit by the DAC roll, but you are decreasing the cost when it does.
For example:
With one big engine, you might have a DAC chance of 30% and a repair cost of 300.
If you replace that engine with six engines that are all 1/6 the size, they each have a DAC chance of 5% and a repair cost of 50.
So there's still a 30% chance that an engine will be hit. But when it happens, you pay 50 to repair it instead of 300.