My girlfriend owns a 95 Civic LXwith about 130000 miles on it. It has been getting horrid gas mileage and I have no idea why. Horrid being around 200 miles to the tank. I have checked everything I can think of. I have changed the fuel filter, gapped and replaced the spark plugs, the air filter, atx fluid. The car still gets awful gas mileage. There are no modifications to the car at all and she only puts 87 octane in it. It has regular oil changes using a Bosch filter with Castrol 10W30. The tires are properly inflated/balanced and the car is aligned. The car has always been very sluggish and you kinda have to get on it up hills but what can you expect with around 70 hp at the wheels and an atx. The only thing I can think of is maybe she just likes to punch it a little too much but I dunno. With a car that weighs so little and with such a small engine 200 miles seems ridiculous. I have run injector cleaner through it with no improvement. It has no issues at all. Besides the horrible mileage the car runs great. It is smooth both in its idle and while driving and in its higher RPM's it pulls suprisingly well. So I dunno. I am at a loss. Any suggestions would be great. Thanks

 

Check the spark timing. If it's late that can kill gas mileage and will also reduce power some.

But it wouldn't be unheard of to only get 200 miles per tank if it's city driving and she is the type to floor it everywhere she goes.

 

WELCOM to HCF I got a few ideas. It sounds like you have tried a lot so

-check catalytic converter for glowing after engine iswarm or egg smell
-timing
-worn rotor,distributor cap or bad coil
-ebrake not fully off
-running cleaner in the tank may have clogged up new fuel filter
-fuel pump
-cylinder compression
-oil flush
-seafoam
-run engine until really warm, fan comes on twice than pull spark plugs out and spray gumout in the hole. it will desolve the junk instantly
-driving harder?
-Bad fuel
-lubrication under hood
-wires

All i can think of right now

 

O2 sensor maybe? i got 3-4 less mpg when mine went last week at 47000 miles.

 

I forgot about 02 sensor , when mind was bad i lost 8 MPG it was horrible! but that cost some$$$

*found out my dash light (engine light) was burnt out

 

when you lose an o2 sensor your check engine light comes on right?

 

The check engine light should come on if the O2 sensor is bad. But make sure that the light works; when you turn the key on but don't start the engine it should come on for about 2 seconds and then go out.

 

Not typically, actually. In fact, most GM cars won't trigger a check engine light when the O2 sensor fails...or is failing.

The first thing to look at when the gas mileage is crap would be the O2 sensor. If it's original, it's immediately suspect.

 

Do a valve adjustment, and get some sea-foam and run it through the vac lines while the car is running. This will clean all of the gunk outta the intake manifold, throttle body, valves, well pretty much everything. $10 per bottle, but its worth its weight in gold.

 

So I checked and the check engine light still operates. A ran some seafoam through one of the vac lines and the thing smoked like someone opened a hole into hell. Seems slightly more responsive but the mileage is still dismal. One more symptom I noticed is that especially when the engine is cold, when pushing the gas pedal it sounds like a stream running or water running through a pipe in a house. Thats the only way I can explain it. It gets more so with more pedal application. Fuel lines? Why would I be hearing fuel run through these? Maybe a clogged line? I didn't run any seafoam through the fuel tank for fear of clogging the new filter but maybe I should and just do the filter again? Its a pretty cheap part and easy to do. What do you guys think.