Hello Moon 11,
My guess is that by being at a lower altitude, you'll have a slightly greater TAS(flying faster therefore less time) which would equate to a greater F/F resulting in more fuel burn !?
While we're on the subject, here are a couple more questions to make you fall asleep:
1) What is higher on a B-747-400, Vmcg or Vmca!?
2) If TOW is limited by an obstacle in second segment,what does that mean !?
3) If you were loading an A/C to obtain max range,would you load it with a fwd or aft CG !?
and finally,
4) During what phase of flight is lift the greatest and why!?
Anyone willing to take a run at these are more than welcome.
See ya.