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.
The history of North Korea began with the partition of Korea at the end of World War II in 1945, and the creation of the Communist-aligned Democratic People's Republic of Korea (DPRK) headed by the former guerrilla leader, Kim Il-sung. In 1950 the Korean War broke out.