We adopt time-series and cross-section methods to analyse long-term relationships between pairs of crude oil prices and assess how physical and institutional factors affect their speed of reaction to exogenous shocks. Using a methodological approach which does not require identifying specific crudes as benchmarks, we show that the overwhelming majority of prices have stable long term relationships. We also find that crudes with physical similarity converge quickly after a shock, while prices for oil produced in OPEC countries are relatively slow to revert to equilibrium after a shock. © 2014 Elsevier B.V.