The invention relates to a method for performing an oil change on a wind power plant, comprising the steps of rotating the rotor (3) to a maintenance position, subsequently draining the oil out of a first variable-speed gearbox (6), filling the first variable-speed gearbox (6) with fresh oil, draining the oil out of a second variable-speed gearbox (6′) that is oriented differently than the first gearbox, and filling the second drive device (6′) with fresh oil. The variable-speed gearboxes each comprise a sump (63) having a first outlet opening (65) and a mirrored sump (64) on the opposite end of the housing thereof having a second outlet opening (66). Thus, the rotor (3) does not need to be rotated further during the oil change. The oil change can be performed simultaneously on several or all variable-speed gearboxes, reducing time and personnel expenses. The invention further relates to a correspondingly designed drive device and to an oil changing device.