A liquefied natural gas system for a natural gas vehicle engine with flow driven by the engine includes dual flow paths through at least one heat exchanger. A return path extends from the dual flow paths to the storage tank, and an engine feed path extends from the dual flow paths configured to couple to the engine. A valve and control system are coupled to the dual flow paths capable of alternating flow through the dual flow paths so that one flow path supplies the engine through the engine feed path while the other flow path pressurizes the storage tank through the return path.