How often (in the winter) and for how long should I drive on the highway, to get the water and other contaminants out of the oil? I drive less in the winter and can go weeks without driving on the highway for any distance, but don't like the idea of all these short trips. My daily drive is about 2 miles of 30-35 mph, one way, so the car hits "warmed up" just as I get there. Work is even closer. So, how long and how often? (Winter temps can hit-20, are generally in the teens)