A fuel-based thermal management system for a gas turbine engine, comprising: a fuel-fluid heat exchange system comprising: a heat exchanger configured to thermally couple a fluid received from a heat source and a fuel received from a fuel source , and a valve configured to regulate a flow of the fluid to the heat exchanger; a controller in operable communication with the valve; and a tangible, non-transitory memory configured to communicate with the controller, the tangible, non-transitory memory having instructions stored thereon that, in response to execution by the controller, cause the controller to perform operations comprising: determining, by the controller, whether a temperature of the fluid is above a predetermined fluid temperature threshold, receiving, by the controller, a dissolved oxygen concentration measurement from an oxygen sensor in communication with the fuel; receiving, by the controller, a first fuel temperature from a first fuel temperature sensor upstream of the heat exchanger; determining, by the controller, an updated dissolved oxygen concentration using the dissolved oxygen concentration measurement received from the oxygen sensor, the first fuel temperature, a flight cycle time, and at least one of an altitude measurement or a ambient pressure measurement; and modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration. a fuel-fluid heat exchange system comprising: a heat exchanger configured to thermally couple a fluid received from a heat source and a fuel received from a fuel source , and a valve configured to regulate a flow of the fluid to the heat exchanger; a heat exchanger configured to thermally couple a fluid received from a heat source and a fuel received from a fuel source , and a valve configured to regulate a flow of the fluid to the heat exchanger; a controller in operable communication with the valve; and a tangible, non-transitory memory configured to communicate with the controller, the tangible, non-transitory memory having instructions stored thereon that, in response to execution by the controller, cause the controller to perform operations comprising: determining, by the controller, whether a temperature of the fluid is above a predetermined fluid temperature threshold, receiving, by the controller, a dissolved oxygen concentration measurement from an oxygen sensor in communication with the fuel; receiving, by the controller, a first fuel temperature from a first fuel temperature sensor upstream of the heat exchanger; determining, by the controller, an updated dissolved oxygen concentration using the dissolved oxygen concentration measurement received from the oxygen sensor, the first fuel temperature, a flight cycle time, and at least one of an altitude measurement or a ambient pressure measurement; and modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration. determining, by the controller, an updated dissolved oxygen concentration using the dissolved oxygen concentration measurement received from the oxygen sensor, the first fuel temperature, a flight cycle time, and at least one of an altitude measurement or a ambient pressure measurement; and modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration. <EOS>