  New measurements of two- and four-particle elliptic flow are used to
investigate flow fluctuations in collisions of U+U at $\sqrt{s_{NN}}$ =
193~GeV, Cu+Au at $\sqrt{s_{NN}}$ = 200~GeV and Au+Au at several beam energies.
These measurements highlight the dependence of these fluctuations on the
event-shape, system-size and beam energy and indicate a dominant role for
initial-state-driven fluctuations. These measurements could provide further
constraints for initial-state models, as well as for precision extraction of
the temperature-dependent specific shear viscosity $\frac{\eta}{s}(T)$.
