We employ a Markov-switching regression model to characterise pricing dynamics in the Western Australian retail petroleum market. We find the existence of Edgeworth price cycles of a similar nature to those recently observed in some other retail petrol markets. Cycles are frequent, asymmetric, and of substantial amplitude. Importantly, we observe cycles in an environment inconsistent with the timing specification of the leading theory of Edgeworth cycles. A recent change in policy imposed a discrete time environment on petroleum retailers in Western Australia, allowing us to rule out the Maskin and Tirole (1988) model. We also discuss episodes of disruption and evolution of the price cycle. (With Hajime Katayama)