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.
On 22 July 1946 Soviet authorities in North Korea established the United Democratic National Front, a popular front led by the Communist Party of North Korea. The Communist Party of North Korea soon merged with the New People's Party of Korea, a party primarily composed of communists from China.