Changes in fuel consumption affect VOC emissions by reducing refueling vapor losses and spillage. Other emissions (such as sulfates) are also affected by fuel consumption. MOVES incorporates changes due to fuel economy requirements that were finalized as of the date of the current release. MOVES does not model any proposed requirements.
Note that changes in fuel economy alone are not assumed to affect tailpipe VOC emissions, since these are a function of emission control technology, not fuel consumption.
MOVES does include other changes to VOC emissions, namely, a change to how methane emissions are calculated reduces the VOC fraction of total hydrocarbons.
For more information about MOVES see: MOVES Onroad Technical Reports.