I average 22, but that is mostly highway (at 70-80 mph mind you). On our trips to the beach which is an 8 hour cruise we were getting close to 27 mpg. That was doing about 65-70 and no dramatic speed changes.
I still think whatever they treat the gas with during cold months and the temp itself eats about 1-3 mpg, but that could also be the added heater and ac/defog adjustments.
2013 S4 Loaded (and NO RFT's) Awesome is an understatement
2008 MT X3
RIP you were a faithful sidekick and will be missed.
2007 AT X3 RIPOS
2000 Jeep Cherokee
1997 Twin Turbo RX-7
1984 GTI Wolfsburg Edition Neuspeed and more