Frank Lee is a superman bike rider though. (Noobs need to be made aware of this to put his responses in perspective. )
GRU: the advice given here is good. (If you're not going to ride a bike... )You need to preheat the engine if you want to reduce fuel consumption.
FYI, my dad got 11 L/100 km / 22 mpg US from his 2006 Corolla automatic (rated 26 mpg US in the city) in similar driving to yours (in winter). See:
http://ecomodder.com/forum/showthrea...rolla-546.html
Also make sure the tires are pumped up, read the 100+ driving tips and save up for that ScanGauge for instant feedback. But you're pretty much driving a worst-case routine for getting good mileage.