Originally Posted by msantos

Yes, in addition to adopting the recommendations that follow, always expect the winter fuel economy to be lower. How much lower? Well, it depends not only on the weather conditions but also on how diligently you follow the recommendations we offer.

Anyhow...

1- Pump up your tires. I suggest setting the rear tires to 38 PSI and the front to 40 PSI as a start. Another popular setting is 40R-42F and even 42R-44F. The higer the pressures the better the FE. Its that simple.
2- Don't warm up idle the car before driving off.
3- Block your front grille.
4- Install and use a block heater
5- Avoid (if possible) gas brands that add ethanol as an oxygenant agent.
6- Use the DWL and DWB technique liberally. The DWL is VERY useful in the first 5-10 minutes of your drive.

Cheers;

MSantos