Its basic human nature that we often want to improve the efficiency of the things we do. Its also human nature to be skeptical when were offered something of value that carries little or no cost: Wheres the catch? What am I giving up to benefit from this largesse? These can be legitimate questions, and they deserve detailed answers, no matter whats being offered. When considering how pilots use the mixture control to manage aircraft piston engines, desires to improve efficiency and healthy skepticism can intersect.