I asked myself "why would anybody fly at best-power doing say 140kt when they can fly at best-economy also doing 140kt, and use less fuel".
Neither Socata nor the dealer (Air Touring) were able to answer.
Prolonged full-power climb with a normally aspirated engine? After all, you'd lean for best power in those circumstances. (And at some altitude, the best you could achieve might be 75% engine power when leaned for best power, but only 65% or 70% when leaned for best economy.)
I think there's an example in the PA28 POH that details the fuel burn calculation for a fictitional flight, taking into account taxi, climb, cruise and descent with all the different fuel burns from the various tables in the book. Climbing is (obviously) done at best power mixture, while the cruise is done at best economy.
On the other hand, the R2160 POH only has instructions to lean for best power, and tables for the associated fuel burn. Due to the incredible crudeness of the mixture knob, resulting in almost immediate rough running if you lean beyond best power, leaning for best economy is virtually impossible and not covered in the POH whatsoever.