Valve oil seal is a kind of oil seal, generally vulcanized by the outer skeleton and fluorine rubber, oil seal mouth is equipped with self-tight spring or wire, for the engine valve stem seal. Valve oil seal can prevent oil into the exhaust pipe, resulting in oil loss, to prevent the mixture of gasoline and air and exhaust emissions, to prevent the engine oil into the combustion chamber. Valve oil seal is one of the important parts of the engine valve group. It is in contact with gasoline and oil at high temperature. Therefore, it is necessary to use materials with excellent heat resistance and oil resistance. It is usually made of fluorine rubber.