The discussion and any calculation of TAT may be too generalized to give a practical answer. The fuel temp in a particular aircraft will depend on many variables such as tank location, structure, location, and any fuel re-circulation. Most aircraft where fuel temp is important will have a fuel temp measurement system. In those aircraft that do not then it is necessary to establish the correlation between the measurement of TAT (including TAT system errors) and actual fuel temp, this is normally established by flight test. Thus, in extreme, it may be possible for the fuel to be colder than the indicated TAT.