Originally Posted by exAC

Contrary to what has been spoken here before.

One does not know if there is a significantly higher burn between the two altitudes unless flight plans have been run and then the two compared. I have seen many many flight plans where going lower only resulted in a minor increase (and once or twice a decrease) in fuel burn.

It all depends on the strength of the upper level winds. Particularly on the return your headwinds might have been considerably less than normal lower down.