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 Korean War began on June 25, 1950, when North Korea, under the communist dictator Kim Il Sung, invaded the Republic of South Korea by sending more than 200,000 troops across the 38th Parallel which divided North from South.