Petroleum refining is the third-largest global source of stationary greenhouse gas (GHG) emissions, accounting for 40 percent of emissions from the oil and gas supply chain. To assess these climate impacts, this study uses a transparent, open-source tool to model 93 percent of the world's oil flowing to 153 refineries across 53 countries. We find that GHGs vary widely based on the oil selected and the refinery used. Our results demonstrate that global refining emissions could potentially be reduced by 11 percent and 58 percent under low-and-high-investment emission reduction scenarios, providing guidance on climate-sensitive refining choices and future investment in emissions mitigation technologies. This study is part of a large research effort — the Oil Climate Index — to assess the lifecycle climate impacts of the oil and gas sector and reduce emissions in line with international climate targets.