Im getting killed with FE now that its winter, a couple things ive learned is that in the first place we all know warm up and keeping all the parts that like being warm, warm, cuts FE, also winter mixes from the oil companies doesnt help either. In winter there are many different additives so that the fuel doesnt freeze. Also, and i dont know if this is related , maybe i can get some advise from you guys. After i took my car in (05prius pkg 4)for its 5000 mile service, not only do i feel my milage went down but it seems louder. Is that just because of the below freezing mark on the thermometer? thanks Dean