To fully evaluate how much fuel is used and the total emissions produced by a vehicle, all parts of the fuel-cycle need to be considered. The Argonne National Laboratory, part of the US Department for Energy, has developed the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) Tool.
The tool allows researchers to evaluate different combinations of fuels and vehicles from the point of view of a fuel-cycle/vehicle-cycle basis.
The tool can be downloaded from anl.gov. Registration is required for use.