HELP: Gas Mileage
 

Okay, I don't really get wtf is going on here but my 96 civic hatch has been getting some terrible mileage for what it is (totally killed the point in gettin this car)

I looked up what the EPA rating was and I should be getting 12.7km/L which is around 570km. I was gettin 420km before and I accepted that considering the age of the car/engine but now I am only getting around 380km. I'm not sure what could be causing such a big drop in mileage, I was thinking it could be my cat cause I got my CEL light on and when I got it checked I was told it was my cat that was causing the issue.

I'm going to try and uses some injector cleaner and see if that helps at all but if anyone has any insight on what I should be checkin please help a brother out

Replace Oxygen Sensor. Possibly it's tripping the CEL. Did you check the codes yourself?

If the O2 sensor is faulty, since the ECU can't read it, it will default to running quite rich. (bad gas mileage.)


Then check the other obvious stuff, like Tire pressure.

Nah, i got mechanic that's a family friend check it out and also a member on this board checked it out for me as well when I bought a rear brake conversion from him.

I have gotten the sensors replaced already and it didn't seem to help

if I can't figure this out soon I might just dump in a b series rather than waste time and money replacing random parts

fuel filter
fuel pressure regulator
fuel pump

are u getting lack of power (i know its a civic but still)
if u are it may be clogged injectors and the stuff mentioned above

so from a full tank til the light comes on you get 380km?

If the O2 sensors are new/working, tire pressure good, etc. Then it sounds like you have incomplete combustion due to ignition problems.

It could be a number of thing,s like poor compression, worn or broken EGR valve, sticking injectors, dirty air filter, shot sparkplugs, valve adjustment? When was the last time you did a full on tune up?

last time I got a full tune up done was 5 months ago also from the same dude

my civic doesnt have a gas light but from full to the red of the E is 380km and it drops crazy fast once I get to half tank. I will get around 250 until half tank and than it will just drop like crazy.

It doesnt feel like I am losing power but like you said its a civic so its a little hard to tell.

I noticed something last time that didn't make any sense to me but maybe someone here will know. I tried switching up the octane from 89 to 92 and my mileage got worst instead of better.

Any help or even a direction to look it would be great.

TIA

My other friends who owns older Hondas also complain that the fuel gauge will drop much faster after the half tank marker.

yeah my 00 civic got 350 from full tank til light on but i was on snow tires.

time to get a new car to pick up jbs in richmond.

If you got your mechanic to diagnose the problem and he is telling you it is the cat.. then isn't it rather obvious that his diagnosis will be more reliable than random number of people who have never seen your car to give you random advice?

Get an OE cat, not some random Chinese/Japanese brand who have more syllables than the amount of catalyst in the converter.

I would be surprised that your "dude" don't charge you 2x next time you see him... especially since you mention he also reads this thread.

Actually your calculation is a bit off

Since honda civic's have 45 litre tanks, you've calculated the full tank.

The light comes on when there is about litres left in the tank which works out to be 480-500km a tank.

Out of curiosity, what octane do you use?

And Godwin has a good point...

hey be happy..i only get 360km/tank highway kilometers too...

Read that gas tank should always be kept above half otherwise it'll lose pressure in the gas tank and not use it as efficiently.
Hence higher mpg when gas tank above half?
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actually you will get worse mileage because your gas tank is full due to the extra weight. The reason your meter goes down faster after half a tank because the sending unit doesnt read the amount of fuel in a linear fashion.

thing is he told me about my cat 4 months ago and I was still getting 420km until about a week ago so I think it has to do with something else as well and just want a list of things I should get checked out or if anyone else has exp this before

normally I use 89 but have switched to 87 since I got better mileage when i used it

WHY would you waste time and money replacing random parts when you already know it's the cat?

Fuck, you're a dumbass. :haha:

because I think its more than just the cat?

Then what's the point of getting a professional opinion?

^
:facepalm: for a few reason.

1. Running 92 octane for no fucking reason.
2. The whole "my trusty mechanic says its this"
3. When you receive advice, you sorta disregard then default back to your mechanic.

Anyway, do some investigation YOURSELF. Find out the codes that the CEL is throwing. Then you should get a much better idea of what's going on.

If your SES light is on, your car goes into a so called 'open loop' or 'limp mode' (depending on the code's thrown) and you will never get much power and your gas mileage goes down the tube.

also whens the last time your car had an old fashioned tune up?

I would replace:
Air filter
Plugs
Cap/rotor/wires
Fuel filter
And an Oil change

this should help a bunch if you haven't done any maintenance if a while.

Umm, no. You're mixing the two lights up.

The Check Engine Light (CEL) is to do with the engine. That does that 'limp mode' shit.

The Service Engine Soon (SES) light means there's something wrong with the car's electrical system... but not necessarily the engine. Usually the body control module picked up a problem somewhere.

all gas stations require up to 10% ethanol in their fuel so that can drop your mileage by 10%