[Grandpa Kim]

Quite right, Oleg, I was speaking of the stock game. I'm not sure about the supply amount for most mods, but it seems to me the efficiency derives from the amount of supplies used to move one sector. In stock, each engine, no matter type or level, uses 10 units of supply per engine to move one sector. I know in Devnull, that amount decreases as the engine level increases. It starts over when you discover a new type. Therefore you can go farther with Ion III than you can with Ion I. I don't know what would happen if you mixed different levels of Ion engines in this circumstance.