While more than 65 percent of the fuel energy is lost as waste heat in the form of hot exhaust gases and cooling water, heat recovery promises one of the biggest fuel economy potential regarding the technologies available in the next 5 years.Applied to trucks, buses or passenger cars, a bottoming Rankine Cycle (RC) on exhaust heat shows a great potential in fuel consumption reduction , even for part loads. Nowadays it seems to be clear that the heavy duty industry will implement RC on their long haul trucks before 2020 as an answer to future stringent regulation and the still increasing customers request for operating cost reduction. A 5% fuel economy is achievable when using ethanol as working fluid on such vehicles. Regarding the expander, developments on either impulse turbine or piston expander are carried out by competitors. For passenger cars where the gain of such a device is still controversial, no clear technological choice emerges.Founded in 2009, Exoès has been developing an axial piston expander accepting high temperature vapor of water or ethanol, whose hot side can run oil-free. We will explain the key points of this technology, our technical options and last simulation and tests results with a focus on gasoline passenger cars.