I spend about $150/month. Your question has so many variables that every answer will differ. Anyone who buys an X for gas mileage and saving money, is buying the wrong car. What I like about the X is it's huge fuel tank. I can easily get 400+ miles per tank which minimizes my trips to the gas station. Granted it costs $60-$70/tank, but I'm only filling up 1/3 the amount of times I was in our 325.