This paper investigates the economic efficiency–oil consumption relationship in 42 countries during the period 1986-2006. In a first stage by using DEA window analysis countries’ economic efficiencies are obtained. In a second stage an econometric analysis based on robust GMM estimators reveals an inverted ‘U’-shape relationship between oil consumption and economic efficiency. In order to capture heterogeneities among countries’ development stages the analysis has been separated into two groups (advanced economies and developing/ emerging economies).