Gas turbine engine thermal management system

A thermal management system (100) for a gas turbine engine (20) includes a first heat exchanger (66) that provides a first conditioned fluid (83), a second heat exchanger (68) in series flow communication with the first heat exchanger (66) and that exchanges heat with the first conditioned fluid (83) to provide a second conditioned fluid (89), and a third heat exchanger (70) in parallel flow communication with the second heat exchanger (68) and that selectively exchanges heat with the first conditioned fluid (83) to provide a third conditioned fluid (93). The second conditioned fluid (89) and the third conditioned fluid (93) combine to provide a mixed conditioned fluid (95). A first portion (97) of the mixed conditioned fluid (95) having a first temperature is communicated to a first engine system (110). A second portion (99) of the mixed conditioned fluid (95) having a second temperature is communicated to a second engine system (118). The second temperature includes a greater temperature than the first temperature.