"Marco Leon" wrote
747-400's are actually more efficient in cruise on two engines.

I know that to be not true. The maximum cruise altitude on two
engines is too low.

While I do not have a B-747 Flight Manual in front of me, I do
have the numbers for its predecessor, the B-707, which are
representative for four engine jet transport altitude vs fuel
flow comparisons.

At a mid-weight for an ocean crossing, 260,000#, the numbers are
for maximum altitude and nautical miles per 1000# of fuel burn.

Four Engines.....FL370 37.9 nm/1000#
Three Engines....FL300 33.5 nm/1000#
Two Engines......FL140 25.0 nm/1000#

It's the two engine maximum altitude that kills you.

Lets see your numbers

Bob Moore
ATP B-707 B-727
PanAm (retired)