Life-cycle emissions of direct greenhouse gases (GHG) have been calculated to elucidate the global warming impacts of various fossil fuel feedstocks. Calculations were made for the transportation sector using five fossil fuel sources: natural gas, light crude oil, conventional heavy oil, crude bitumen recovered through in-situ steam stimulation, and crude bitumen recovered through mining. Results suggest that fuels sourced from light crude oil have the lowest GHG emissions, while conventional heavy oil has the highest GHG emission levels for this application. Emissions of methane can constitute a significant portion of the life-cycle GHG emissions of a fossil fuel. For all the fossil fuels examined, except conventional heavy oil, GHG emissions associated with their production, transport, processing, and distribution are less than one third of their total life-cycle emissions. The remainder is associated with end use. This confirms that consumers of fossil fuel products, rather than fossil fuel producers, have the most leverage to reduce GHG emissions. 2 figs