13-19 isn't normal, this car should get around 25 mixed.
Hondas really aren't what they used to be, I have a firm conviction of that. I worked at an independent shop and the car we had towed to our shop the most was by far newer Hondas 01-07.
One day we had a line of 11 Hondas outside our garage, and I had to push every single one into the bay, because none of them ran.
I hate newer Hondas. I think they are utter crap and should be treated like the plague.
If the poor mileage Accord is being driven by a "left foot braker", that may be the problem: so many of those drivers "rest" their left feet on the brake pedal.
In driving to and from work, I am astounded by the amount of brake lights I see. Then I read on here of people requiring new brake pads at ludicrously low mileages (such as 20,000-30,000 miles) and I can see why. My wife and I are both excellent drivers, and never, ever ride our brakes. Her large SUV just passed 100,000 miles on the original brake pads, which have at least another 15,000 miles left on them. The very earliest I have ever replaced brake pads on any car is 70,000 miles, and that car was a business vehicle used almost totally in city traffic. If people ride their brakes, they will get very low fuel mileage and replace brakes at ridiculously short intervals such as 30,000 miles. Learning to drive saves a LOT of money.
I have a 1999 Honda 2 door Accord with the 2.3 liter 4 cylinder, and I'm getting 26 miles to the gallon with 200000 and a heavy foot. I can put 5 dollars in my tank bone dry, and go two weeks. For you I'd recommend a set of new O2 sensors, a new catalytic convertor and an EGR valve; those are the main problems with every Accord, and they seriously affect your car's performance and fuel economy.
My experience with Honda was all bad. It was poorly built and very unreliable. We now drive only solid and reliable Ford and GM vehicles. We don't have the time or money to waste repairing cars.
I never got high mpg with the VTEC6, and it required 93 octane fuel. I did not rest my left foot on the brake. And speaking of brakes, why did my rear discs wear out faster than the front discs? Wait til you have to buy xenon bulbs or 2 for your Honda. Not an economical buy.
I have a 1992 carburetor Accord (2.0 L) with an automatic transmission. It is my first car, and the first automatic transmission car I have driven regularly. My family had four Peugeots, and then went to Japanese cars for reliability.
I have driven my mother's Peugeot 505 a lot, and I knew it very well. With a 2.0L, 8-valve, carburetor engine, 5-speed manual transmission, I used to get 18 MPG (13 L / 100 km) from it, strictly city driving.
The Accord is a little heavier, but it has a theoretically more advanced 16-valve engine. So I expected similar fuel economy. According to the manufacturer, the Peugeot 505 automatic does 15 MPG (15 L / 100 km), so I expected a similar fuel economy from my automatic Accord. But instead I get 14 MPG (17 L / 100 km), if not worse. Traffic conditions have changed; there's a lot more traffic jams than when I used to drive my mother's 505, so I began to blame the demographic change for my poor fuel economy. But now I realize that in an automatic-transmission car, I use the brake pedal a lot more than with a manual-transmission car.
And there is the issue of brake rotors: I changed them, and six months later they are warped. We never changed brake rotors in a Peugeot. But they were all manual transmission cars. Many, many years ago I was a mechanic in a Honda dealership, and now I remember that one of the old guys who was training me told me that I should check the brake pads in an automatic transmission Honda more than in a manual transmission Honda. And it is true, the more you use the brakes, the more you waste fuel. Maybe my driving style has something to do with it; maybe I did not perform the transition from manual-transmission to automatic-transmission driving as I should.
By the way, I get 24 MPG (10L / 100 km) in highway-driving from my Accord, easily, with the air conditioner on, the family on board, and the trunk loaded, so the problem is city driving.
Thanks for the advice, I will try it.