Hi KLOS
On a B744 (GE) engines the fuel burn is approximately 10 tonnes per hour in the cruise and the optimum flight level, ignoring wind effects, increases at about 700 feet per hour. On a typical day, say westbound, you might start at say FL330 as you enter the oceanic area west of Ireland and exit the ocean over Newfoundland at FL350...if ATC will give the level!
Hope that helps.
regards
BBK