A waste heat recovery system is provided for an internal combustion engine having a piston, a cylinder and an intake manifold, significantly improving gas mileage efficiency without reliance on alternative fuels. The system includes a heat loop having a heat transfer fluid, a compressor in fluid communication with the intake manifold to supply compressed air thereto, a Stirling engine operated and optimized via thermal communication with the heat loop, and operatively coupled to the compressor. The system includes a chiller in thermal communication with the heat loop, and with the intake manifold to cool the compressed air communicate to the cylinder. The system may include additional Stirling engines operating other devices, or being operated by a device, such as a propeller. A vehicle can incorporate the system and route fluid to and from a radiator. The system can be used in both portable and stationary applications.