Oil is an essential lubricant in your engine. It lets metal press against metal without damage. For example, it lubricates the pistons as they move up and down in the cylinders.
1 By the time of the Japanese surrender in August 1945, Korea was the second-most industrialized nation in Asia after Japan itself.  But the wartime mobilization of 1937-45 had reintroduced harsh measures to Japanese colonial rule, as Koreans were forced to work in Japanese factories and were sent as soldiers to the front.
This is believed to be a village of a tribe that lived along the Daedong River. No one knows exactly where the Koreans came from or who they are. The humans as we know today, homo sapiens sapiens, came into being some two and half million years ago.