Remember. They change fuel blends for winter months. I live in CA and my fuel mileage has dropped from 58 to 53 when they switched to oxygenated winter blend fuel...
I just don't want to hear most of you complain. Except Jay and a few others. It's -finally- real winter here. It was almost two months late. Yesterday, -26C daytime, -30C was the min. Sat. night. I got up early on Sunday and plugged Pearl in (7:30). By 11:00 the coolant was at +30C when I started the car. In the insulated but unheated garage it was -7C. Yup, I got poor mileage. Nope, nowhere near as poor as -every- other car on the road. I was running around 6.5 l/100 km. Pearl never fully warmed up, in fact, she never got to stage 4. I only drove 7 km each way though. Day before, I drove 20 km in similar temps. and got the coolant up to 70C once (highway section). Prius is just too efficient!