I have a 2005 prius and just like clockwork harsh cold winter drives in chicago and buffalo reduce my mileage into the 38/42 mpg range. Alas then comes spring and just like that i am back to my 44/48 mpg range. In mild weather when i drive very conservatively i have hit 50/55 mpg for some short stretches ie a 20 mile one way trip, but the bottom line is keep on driving conservitive, sit back and watch all the crazy people darting in and out and cutting each other off and wasting fuel and loosing their cool along with their cash its a hoot.