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In general, the oil forms a continuous film of oil between the two contact faces. This oil film acts as a liquid lubricant - preventing direct contact between the metal and the metal, thereby reducing friction. Whether the lubricant can provide liquid lubrication depends on whether an oil film that does not break on both metal surfaces can be formed. When this layer of oil breaks under heavy load, it will cause resistance and friction.China Jining Changsong Diesel Engine Oil SAE 15w-40 15W40
