In all of the cases considered, the highest efficiencies are predicted for when the rates of all the forward processes are approximately equal, leading to a cycle with no single rate-limiting step. Rate-limiting mechanical steps promote futile cycles, in which fuel is consumed without taking a forward step, as the unfavorable fueling reaction is kinetically favored over shuttling, decreasing both current and efficiency. Rate-limiting chemical reactions decrease the information flow in the steady-state since fast shuttling hinders the generation of a concentration bias compared to mechanical equilibrium, resulting in lower thermodynamic efficiency without reducing current or substantially changing fuel consumption per cycle. The strong dependence of efficiency on shuttling rate indicates that, like macroscopic engines, the efficiency of a motor will be dependent on the load it is working against. To use molecular machines most efficiently, they must either be tailored to the job they perform -such as using diesel engines for heavy loads -or they must use the equivalent of gears for macroscopic engines, to ensure they are working under optimal conditions.