According to quantitative studies, oil seems the only natural resource that is robustly linked to civil war onset. However, recent debates on the nexus of oil and internal conflict have neglected the fact that there are a number of peaceful rentier oil states in existence. Few efforts have been made to explain why some oil-exporting countries have experienced civil war while others have not. We thus address this puzzle, by arguing that civil war risks depend on the specific conditions of oil production and how they come to structure state–society relations. Specifically, we expect that states that are either highly dependent on oil or who have problematic relations with oil regions are prone to civil war. However, these risks will be mitigated either when democratic institutions can manage conflicts peacefully or when abundant oil revenues can be spent in such a way as to buy peace. We test this conditional argument by comparing 39 net oil exporters, using a (crisp-set) Qualitative Comparative Analysis – a methodology particularly suited to test conditional relationships in medium-N samples. Our results largely confirm our conditional hypotheses. Conditions of oil production are ambiguous, and particular combinations thus explain the onset of civil war. Specifically, we find that high abundance is sufficient to ensure peace, while two distinct pathways lead to civil war: the combination of high dependence and low abundance, as well as the overlap of ethnic exclusion and oil reserves in non-abundant and non-democratic oil states.