queensny

Hi everyone,,
Looking for some help/advice here.
I am looking to help out my friend who recently purchased a 98 Civic DX.. Nothing special, the price was right..
However upon driving for 2 weeks we’ve noticed that the car is very poor on gas mileage. This is an all stock (absolutely no mods) have been done. Very basic car and only getting about 20-25mpg..
We’ve gone synthetic on oil, replaced the stock air filter..New radiator (old one had crack), replaced tranny oil with (Honda OEM Tranny oil)… and idles smoothly no problems..
But still no love….
Any advice based on experience or knowledge as to what other steps we could take?
would replacing the fuel filter help?

S2Integra

dirty injectors, manifolds, plugs, and/or combustion chambers. fouled O2 sensors, and yes fuel filter. Try to imagine the fuel traveling from the tank to the cylindar, how many things along the way can cause restriction, same with air intake and exhaust. Or poor spark as well.

macson

^^^those above. Basically start looking at your typical "tune-up" parts. I've personally had poor milage due to a bad PCV valve and shitty spark before.

civic_r87111

S2Integra covered all the bases, most common things to affect MPG is distributor car, plug wires, plugs, air filter, fuel filter, gummed up and dirty air ways, injectors, and the O2 sensor. Usually if it is a sensor problem it will cause a code in the ecu, so I would say at least pull the plugs, inspect them and check the gap, replace the fuel filter, and do some sort of a fuel system cleaning. Oh and yes the PCV valve that is often over looked as macson pointed out.

steviezee47

Check tire pressure also

Jimster480

Run some techron through there along with Chevron gas at the same time (if its available in your area). Change the fuel filter & spark plugs, check the spark plug wires. Like steviezee47 said, check tire pressure. You also need to check/replace the PCV valve.

queensny

Fellas, all the above help/advice is most-most appreciated..
I will do the fuel filter this weekend and check the spark plugs.
Anyone ever used a product called “”SeaFoam”… It’s a bit of an old-school looking product that Ive used in the past.. If the formula doesn’t change I am going to use that in a full-tank to help clean out the injectors and buildup..
If anyone has used other products to clean injectors that have shown good results,, please let me know…
Thanks again..

Jimster480

Yes seafoam is an option to clean out everything. But first you should change/check the parts that can be bad.

Townson

try some gumout fuel injector cleaner.

Jimster480

Techron is better than Gumout.