Ah, so maybe their models are just too simple? The 40-50 band being more efficient isn't just a function of stopping frequency -- you can directly measure it o

Ah, so maybe their models are just too simple? The 40-50 band being more efficient isn't just a function of stopping frequency -- you can directly measure it on your favorite long, stop-free stretch of road. Your engine has a nonlinear efficiency with respect to throttle position and load, and at low speeds those dominate fuel economy rather than increased air resistance. An engine optimized for efficiency would of course drive as slowly as possible, but other factors also contribute to the design of modern car engines.