Abstract Planetary gears are used in several applications given that they provide high reduction ratio in a compact size. Two kinds of lubrication are used in these applications: injection or splash lubrication. In case of splash lubrication, the authors already highlighted the importance of the centrifugal effects leading to the formation of an oil ring inside the reducer, therefore giving a method to compute churning power losses. In this paper, another flow regime is underlined when centrifugal forces are not sufficient to turn the oil sump into a ring. In addition to this observation, an in-depth analysis is given regarding the dependence of the churning power losses with operating conditions and oil characteristics.