75/76 Dodge Dart /6 average MPG and improvements

Yeah, with the terrain around here varying extensively between flat land and light hills, and the winters being Ontario winters, Il likely have to do plenty of maintenance. Any of you running your cars through the winter? What would be your first recommendation for someone in an area that has four drastic, equally back breaking seasons? My original question still stands, but so does my statement that I can probably use all the insight I can get.