Purchased a 1998 Civic EX 3 months ago, and it's only averaging between 23-25 city and 25-29 hwy. New Parts I installed:

1) Manifold
2) Autozone Brand Gold distributor cap and rotor
3) NGK wires and copper plugs
4) Fuel filter (firewall)
5) Air filter
6) Driver's side CV replacement
7) O2 sensor (top: engine side)
8) Oil filter and oil

Parts I serviced/cleaned:
1) Manual Transmission Oil drain and fill
2) V-tech Solenoid + gasket
3) Distributor O-ring
4) Ignition Timing (light)
5) Cleaned all ground connections
6) IAVC Valve
7) Throttle Bottle
8) Re-tensioned throttle link
9) Replaced PCV valve
10) Sea-Foamed
11) Valve-Lash Adjustment
12) Tires inflated to door stamp recommendation 30psi

Front rotors rub slightly against pads, was told that this is normal by local mechanic. Back wheels spin freely with slight resistance against shoes.
Seems to coast fine in Neutral.
I have a concern that the catalytic converter may need changing but, no rattling or engine stalling or rich fuel smell.

Very frustrating, as others are posting over 30 MPGs. City driving I average just over 200 mpgs on a tank full to near empty. nearly 300 mpgs on full tank to near empty highway. Another issue I feel is the fuel tank baffling (lack of) and possibly not-so accurate fuel gauge, as it floats on corners and hills.

At this point I have a love-hate with the car. Love driving it and learning how to service it. Hate the gas mileage.
I do plan to get a complete timing belt kit (timing belt, tensioner, water pump, cam seals, AC + steering pump belts) soon, so that may help if the car has ever jumped some teeth before I bought it.

update: revving the engine (in neutral) around 5000 RPMs the engine starts to jump and makes a knocking sound.

All replies appreciated.

 

whats the mileage what size rims do you have do you have a system in the car. that mileage really isnt that bad consindering the age of the car.

 

thermostat? if the engine is not reaching proper operating temp(around 200*F), you would be burning unnecessary fuel.

Also, I have seen a timing belt be off 1 tooth and cause poor fuel mileage. Have you verified correct ignition timing?

 

Standard rims. Stereo system?. 122,000 miles.

 

I read about engine temp on other post. Seller didn't have records but, looks like radiator is fairly new and usually a new thermostat would be put in at that time. Car warms up quickly, and temp needle is a little more than 1/3 way up.
Does Autozone do digital temp readings?

I have a strong feeling timing belt has skipped. When I rev up the car in neutral to about 5000 RPMs the engine starts to jump.Could be a motor or tranny mount except I've revved it a bit in 1st gear with E-brake on and it didn't lift.