Abstract: Provided is a composition for cleaning and coating of the inside of internal combustion engines and cleaning and coating metallic surface of rotating parts and sliding parts of the engines which contains a zinc phosphate, a solvent, a surface active agent, a natural vegetable oil and a mineral oil as components. This composition diminishes friction applied to rotating parts and sliding parts of internal combustion engines and diminishes friction loss by cleaning and coating and, in addition, reduces causes for incomplete combustion in combustion chamber to improve performance of engines and inherent performance of internal combustion engines. Further provided is a method for cleaning and coating of engines using said composition.