I have a 42 mile commute each direction, with most of it at freeway speeds. On any given week I average no worse than 38 MPG, usually in the 38 - 40 MPG range with the MPG getting better the slower the traffic gets. If I drive the car on errands around town it *always* does better than the commute. Cold weather has no effect, though it doesn't really get that cold in Northern California. Joe