A servicing device and more particularly an oiler or a filter device, for the preparation of a pressure medium, which comprises a capacitive sensor having at least one first electrode responsive to at least one operational parameter of the servicing device. An expendable material and more particularly a filter means or an additive for such a servicing device, which is renewable and is able to be utilized by the servicing device for the preparation of the pressure medium and bears a capacitively detectable code means, on the basis of at least one operational parameter of the servicing device is detected. Furthermore there is a capacitive sensor for such a servicing device.