Responses
lol... ikr.. maybe the mangaka doesn't know that Japan imports more than 80% of oil. And Japan doesn't have industrial raw materials as well. So actually they shouldn't really flaunt their technology like that.
It was necessary though to establish negotiations with other countries in the new world given that they are a literally a lone island with no support, no ties with the countries in earth.. They have to fend for themselves if they want their country to suvive and besides they might find new sources out there which they can procure
From the looks of things, you would think they would try to conserve fuel better with being transported into a mysterious place