I learned about this "lean-burn" concept as a pilot; Turns out that Lindbergh discovered it in the Pacific theater flying P-38s [1], the idea being to increase manifold pressure, use lower RPMs, and lean mixture. Pilots ferrying airplanes across oceans do it by cruising at, say, 10,000' on a very lean mixture, then slowly descend to a lower altitude; the engine starts running much cooler and sounds like hell (the timing issue the video mentions) but they get great mileage.
[1] https://www.quora.com/Did-Charles-Lindberg-help-WWII-pilots-...