This has been tried before several times (apparently). You are probably seeing the fuel consumption dropping because your mass is dropping as you burn fuel.
Ah ok I haven't thought of that extra factor. Nice catch! So it will allways calculate the fuel amount required for the jump, based on the initail distance between two systems? So no matter how much distance I cover in SC I will never be able to perform a jump if the distance is even 0.01 lys larger than the largest possible distance my ship can jump (72.5 Lys in my case). So if a system is 72.51 Lys this means I have to use jumponium to get there? Do I understand correct?
True, but it takes fuel from your reserve tank, not your main tank, as all module do
But I thought all modules (that consume power that is, i.e. all those with a % fo energy consumption next to them i.e. not those below cockpit canopy in the right panel) are always using fuel from your reserve tank not your main tank. Only when your reserve tank dries completely it refills from the main tank. I am confused..