Turning the analysis on its head and starting from the-recession-did-it hypothesis is much simpler.
What else is relevant to the recession's impact on ground transportation aside from ...transporting things, i.e. Vehicle Miles Traveled? VMT declined about 3% since 2007, while US all-oil consumption fell ~15% (21.8 mbpd to 18.1 mbpd). So place 20% of the consumption decline on recession but the rest lies elsewhere.
Nice piece of work on the possibilities from fuel economy increase, but I don't see it as exhaustive. There may well be other fuel economy impacts, and then there are any number of other areas where oil may be on the decrease:
1. New England heating oil. New England has been one of the last hold outs for oil heat. There's a news report out there claiming the Maine oil heaters cut consumption 45% over the last several years by insulating and switching to other heat sources like heat pumps and high efficiency wood stoves.
http://bangordailynews.com/2011/11/13/business/maine-heating-oil-use-dropped-45-percent-between-2004-and-2009/2. Plastics chemical feedstocks. Has been primarily oil; is now rapidly switching to natural gas sourced ethane. E.g.
http://www.dow.com/texas/freeport/news/2012/20120419a.htmhttp://www.marketwatch.com/story/dow-to-build-new-ethylene-production-plant-at-dow-texas-operations-2012-04-193. Driving behavior. Perhaps as simple as a higher price encouraging people to keep the foot off it, or fleets and investing in fewer-stops software and the like.
4. Natural gas vehicle use up a third by consumption of gas, i.e. that's VMT coming from gas not oil.
http://si.wsj.net/public/resources/images/IV-AA198F_Trans_G_20120614160604.jpg 
