A fuel and thermal management system for delivery of fuel to an engine, comprising: a fuel supply line in fluid communication between a fuel tank and a fuel inlet of the engine; a first heat exchanger comprising a first section in fluid communication with engine oil and a second section in thermal communication with the first section and in fluid communication with ambient air; a second heat exchanger comprising a third section in fluid communication with the fuel line, and a fourth section in thermal communication with the first section and in fluid communication with engine oil, wherein the fourth section is in fluid communication with and downstream of the first heat exchanger section; an engine oil bypass conduit in fluid communication with the engine oil upstream of the first heat exchanger and with the engine oil downstream of the first heat exchanger and upstream of the second heat exchanger; an oil bypass valve in fluid communication with the engine oil upstream of the first heat exchanger, the oil bypass valve configured to selectively distribute a flow of engine oil between the first heat exchanger section and the engine oil bypass conduit; a control valve in fluid communication with the second heat exchanger section of the first heat exchanger configured to control a flow of ambient air through the second heat exchanger section; characterized in that the system comprises an oxygen sensor in fluid communication with the fuel supply line for measuring dissolved oxygen content in the fuel; and an electronic controller configured to set a position of the oil bypass valve and/or a position of the control valve during operation of the system in response to: dissolved oxygen content of the fuel; and temperature of the engine oil and/or the fuel at the second heat exchanger. a fuel supply line in fluid communication between a fuel tank and a fuel inlet of the engine; a first heat exchanger comprising a first section in fluid communication with engine oil and a second section in thermal communication with the first section and in fluid communication with ambient air; a second heat exchanger comprising a third section in fluid communication with the fuel line, and a fourth section in thermal communication with the first section and in fluid communication with engine oil, wherein the fourth section is in fluid communication with and downstream of the first heat exchanger section; an engine oil bypass conduit in fluid communication with the engine oil upstream of the first heat exchanger and with the engine oil downstream of the first heat exchanger and upstream of the second heat exchanger; an oil bypass valve in fluid communication with the engine oil upstream of the first heat exchanger, the oil bypass valve configured to selectively distribute a flow of engine oil between the first heat exchanger section and the engine oil bypass conduit; a control valve in fluid communication with the second heat exchanger section of the first heat exchanger configured to control a flow of ambient air through the second heat exchanger section; characterized in that the system comprises an oxygen sensor in fluid communication with the fuel supply line for measuring dissolved oxygen content in the fuel; and an electronic controller configured to set a position of the oil bypass valve and/or a position of the control valve during operation of the system in response to: dissolved oxygen content of the fuel; and temperature of the engine oil and/or the fuel at the second heat exchanger.