A waste heat recovery system that efficiently converts waste heat from an engine coolant and an engine exhaust in a vehicle. The system includes a coolant heat exchanger that receives heat from the engine coolant, an exhaust heat exchanger that receives heat from the engine exhaust and an economizer heat exchanger. A plurality of valves control the flow of the fluid in different modes as determined by a power ratio between the heat provided by the exhaust heat exchanger and the heat provided by the coolant heat exchanger, including an economizer heat exchanger after coolant heat exchanger mode at low power ratios, where the fluid from the pump flows to the economizer heat exchanger after the coolant heat exchanger and an economizer heat exchanger before coolant heat exchanger mode at high power ratios, where the fluid from the pump flows to the economizer heat exchanger before the coolant heat exchanger.