Abstract: A sealing device for securing an oil plug in threaded engagement with the oil pan to prevent inadvertent loss of lubricating oil therefrom. The sealing device includes an elastomeric washer that underlies the bolt head of the oil plug, a partially closed-ended cylindrical sleeve that surrounds and is integral with the washer, and a cap that is interconnected to the sleeve by a membrane. The sleeve has a protruding lip extending about its upper periphery that interlocks with an abutment extending inwardly from an upper peripheral portion of the cap. Once engaged, the cap prevents the oil plug from being tampered with and from inadvertently dropping out.