US Patent 9810565 Oil level gauge device

An oil level gauge device in which an oil level gauge is inserted in a guide pipe communicating with an oil pan, is provided. In the oil level gauge, a cap having a plug configured to fit on an inner peripheral surface at one end portion of the guide pipe, and a flange integrally formed with the plug and abutted with the one end of the guide pipe, is provided. A groove extending from a deeply inserted side of the plug to an abutment surface of the end abutting the flange is formed in the inner peripheral surface. When the plug is fitted on the inner peripheral surface, a ventilation passage for communicating the inside and outside of the oil pan through the guide pipe is formed between the plug and the guide pipe by the groove.