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.
Caption Time -- Korea 1950-1953. June 25, 1950: The North Korean People's Army invades across the 38th Parallel. The South Korean people simply say 6-2-5 (pronounced yoo-gee-o), June 25th, (see above in Hangul) to remember the beginning of the war that divides their homeland to this day.