Fuel Mileage

No, this is normal. The colder temperatures require the use of more fuel. Heat is what enables the engine to produce power and the colder environment steals some of that heat. Also, the oil is a little thicker when colder, causing more drag which results in higher fuel consumption. The oil pan is also a very good source for cooling the engine, and that heat is taken from the oil, which results in thicker oil in the winter than in the summer, hence lower MPGs in the colder weather. I was on a long trip a couple weeks ago, and the weather was nice when we started and very cold a couple hours into the trip. The real-time MPG indicator in the car was reading several MPG lower in the cold temperatures, even thought the traveling was still normal highway speeds.