  We perform the first study of holographic heat engines where the working
material is a rotating black hole, obtaining exact results for the efficiency
of a rectangular engine cycle. We also make general considerations in the
context of benchmarking these engines on circular cycles. We find an exact
expression that is valid for black holes with vanishing specific heat at
constant volume and derive an upper bound, below the Carnot efficiency and
independent of spacetime dimension, which holds for any black hole of this
kind. We illustrate our results with applications to a variety of black holes,
noting the effects of spacetime dimension, rotation, and higher curvature
corrections on the efficiency of the cycle.
