your car is rated at 18 city and 26 hwy according to the govt. 20 is 1mpg lower than rated combined. drive slower with lighter accel and if you've driven 60k miles without changing the plugs, pull them and replace them.

 

The 2006 Accord has iridium spark plugs that doesn't generally require replacement until around 105,000 miles, unless they are fouled.

 

If this helps the thread any I have an 06 V6 6spd and get 23-25 in the city... also, depending on how heavy on the pedal I want to be I have seen a low of 21 mpg. I get on the hwy 30-32mpg. I haven't changed the plugs since I bought it back in August of 11. I haven't seen any paperwork on the plugs ever being change either and there was a folder of records when I bought it. The car has 126,300 miles on it. I guess you can base your MPG on what I am getting, even though you will slightly get a lil less being an auto.

 

If no CEL, I recommend to do the ff one at a time or after 1 or 2 full tanks, see if your mpg will improve:

1. Clean your catalytic converter – you can take it off or add a gallon of pure thinner in half full tank (google the procedure on how to clean this part and do what you prepared) I have tried the thinner and its work, get better acceleration and mpg.
2. Tune up – replace distributor cap, rotor, plugs, wire, and air filter.
3. Tire pressure - depends on your tire, mine I have the stock 14’ rim, I put 36 psi on front and 32 on the rear.
4. Brakes – see if the brakes are sticky, after you drove for about 5 miles or so and then touch all 4 wheels, be careful they might too hot to touch in that case most probably you have a sticky caliper.

These are the things that I think off, maybe someone can add.

Goodluck.