I decided to get rid of my 2014 Civic EX coupe. But, it got great fuel mileage all the time. I get up to about 36 mpg on the road, and 34 mpg mixed town and country. I drove it about 7,000 miles. I don't own it anymore.
I traded it in for a new 2015 Civic EX-L coupe. Even though the EX-L is new, less than 2,000 miles, I've been getting nearly the same mileage that I got with the EX. Of course, I live on the coast where it's never really hot or cold, and only a little above sea level. If my EX had gotten poor mileage like yours I wouldn't have bought another one. Something is wrong with yours.