Fuel Tank - extended range
 

I am looking to extend the range of my 2014 Civic sedan. What are the options? Fuel mileage is good 35 - 40 mpg depending on the time of year but I'd like to get > 500 miles on a tank rather than the 400 I am getting now. When it gets cold a 400 mile range on my current tank is just not enough for my weekly commute.