Why does it matter if the coating is removed by Valvoline Restore and Protect? The coating isn't the seal and there is no consequence to the coating removal IF it is occurring. There's no way that loose coating is floating around your oil pan.To speed up the test and determine if Valvoline Restore and Protect actually softens the black coating. With the drain plug installed the black coating is torque to specification which may lead to softening of the material.