We're using less oil!
All our upgrades have been paying off. Change in our oil consumption, in gallons/heating degree day, before and after insulating the the hall and tweaking the heating system:

• December 2009, 10.3
• December 2010, 10.8
• December 2011, 5.4

That's a reduction of roughly a half, even after allowing for a mild December. For all of 2010, we bought 2,024 gallons, so the savings will be considerable. Thanks to all who have helped!