A Rankine cycle system including a Rankine cycle working circuit and a lubrication circuit is disclosed. The lubrication circuit and the Rankine cycle working circuit include a shared segment including a mixture of Rankine cycle working fluid from the Rankine cycle working circuit and lubricant from the lubrication circuit. A separator receives the mixture of Rankine cycle working fluid and lubricant from the shared segment and separates the Rankine cycle working fluid from the lubricant. The separated Rankine cycle working fluid is directed along the Rankine cycle working circuit from the separator to the heating zone and the separated lubricant is directed along the lubrication circuit from the separator to a mechanical expander. The working fluid and lubricant are recombined after passing separately through the expander and are then introduced to the condensing zone.
GOVERNMENT LICENSE RIGHTS
 This invention was made with government support under Contract No. DE-EE0005650 awarded by the National Energy Technology Laboratory funded by the Office of Energy Efficiency & Renewable Energy of the United States Department of Energy. The government has certain rights in the invention.