Example systems and methods for integrating an air-cooled oil cooler into an inlet frame of an engine are provided. An example gas turbine engine comprises an inlet frame including an inlet plenum at a first end of an inlet frame flow path, the inlet frame defining an airflow entrance to a compressor; the compressor to provide an airflow through the inlet frame; a pump to circulate a fluid; a plurality of struts supporting the inlet frame flow path; and a fluid core connected to the pump and built at least partially into the inlet frame of the gas turbine engine, the fluid core to route the fluid through the inlet plenum.