An oil cooling system

A system (100) for cooling one or more circulating flows of oil (110), the system comprising: one or more fuel-oil heat exchangers (113), the fuel-oil heat exchangers using fuel for an engine (111) to cool at least one of the one or more circulating flows of oil; and a fuel return line (150) in flow communication with a point downstream of the fuel-oil heat exchangers and a point (151) upstream of the fuel-oil heat exchangers, wherein the fuel return line is arranged so that at least a portion of the fuel exiting the fuel-oil heat exchangers may be diverted to the point upstream of the fuel-oil heat exchangers. Furthermore, a system (100) for cooling a circulating flow of oil (110) may comprise one or more fuel-oil heat exchangers (113) and one or more air-fuel heat exchangers (146', 146"), the fuel-oil heat exchangers using fuel to cool the circulating flow of oil and the air-fuel heat exchangers using air to cool the fuel.