When it comes to fuel conservation, you should consider whether you want
time aloft or distance covered. The choice determines how you conserve. If
you are going for distance, you must consider the most efficient operation
of the engine along with the winds aloft. If there is a headwind, you will
want to go faster than normal optimum range.

When you run out of fuel in the middle of a big ocean, it is often more than
just knowing how to get 3% better fuel economy.

Colin