In my auto 97 Civic EX, I get about 30-31 MPG, so that is filling up around 7 gallons between 210-230 miles. O2 sensor can really kill fuel economy, but there are about a million other things that can also cause it (just general tune up items). My old car had a small air leak in the intake that threw the whole computer off.

 

also check you fuel filter

 

thanks for the advice everyone, just to expand on my problem, yes the CEL is on, and no i have not put any performance parts in my car, and my gas sign never comes on as well, first time i got it i let it run to see when the gas light would come on and sooner or later i hit an empty tank lol..but yea, CEL is on, and o2 sensor needs to be changed, any other ideas? and any idea how much this would cost to fix?

 

1) Have you pulled the CEL codes recently to know whether more than just an O2 sensor code is being thrown? Is the CEL code for the primary or secondary O2 sensor? As Reaper suggested, if the code is for the primary O2 sensor, first fix it and then go from there. The primary O2 sensor is required for the ECU to determine the optimal air/fuel ratio for the engine. If the O2 sensor/circuit does not work, the ECU will use a predetermined air/fuel ratio that is very rich (=low gas mileage).

2) Calculate your actual gas mileage as I mentioned.

3) Do you have an automatic or manual transmission? This too affects gas mileage, with the automatic being much less fuel efficient particularly in city driving.

 

sheesh, i thought that my 280 was bad

 

It depends on how I drive it. Driving aggressively I get 28 mpg. Driving nicely I get 34 mpg. Long freeway rides I get about 38 mpg

I have a 99 EX w/manual tranny

 

i've only had my LX for a couple of weeks, and so far i'm averaging around 31 MPG. I'm using the a/c most of the time cause it's oppresively hot here. and that's a mix on city/hwy. I'm looking to improve my numbers by getting the plugs/wires/etc. plan on doing that probably this weekend.

 

i get about 42-44 mpg depending on how i drive i love my vx motor