Fuel Heating
I am surprised this has not been more in the forefront of thoughts. I cannot say specifically for the B747SP, but certainly for the "classic" B747 and going back a few more years, the B707, they had dedicated fuel heaters. these were switched on by the flight engineer if he had a Fuel Filter Block warning light. After a set period of time, the fuel heater was switched off.
Looking at the diagrams on this thread, fuel heating is only supplied by the Fuel/Oil heat exchanger.
Just a thought ....