Fixation of a toner on a print is achieved, among other things, by rolling a heated fixing roller with pressure on the print and reliably joining the toner in this way to the print. In order to achieve reliable separation of the fixing roller from the print, a fixing oil subsequently also referred to in general as a fixing aid, is often applied to the fixing roller. A shortcoming is that the fixing oil is taken up in an undesired manner by the printer, and covers parts of the printer. Because of this, the printer result is also adversely affected, if the fixing oil reaches the printed image. Cleaning passes of the printer, to free it of the fixing aid, are therefore prescribed in the prior art. However, it is unspecified when and whether a cleaning pass is necessary.