I'm starting to get less gas mileage...?

Ok, so I'm going to put it simple. What are the top 5 reasons my 2002 civic is starting (or at least is appearing) to get less gas mileage. I believe the car was rated at 32/38 but now it seems like every time i put 10 bux in, I get about 5 bux worth, seriously like 22/28. its really starting to suck. And i don't think it's my imagination. What could be the problem here? Air filter, spark plugs, tires, etc. And i'm not gonna go get it diagnosed by some honda guy, either. any help will be much appreciated!!

thanks guys

car has under 55,000 if that matters.

[pdiggitydogg]

spark plugs going bad/gap is off
cat is getting full/going bad (doubt it)
fuel filter is dirty dirty dirty
clogged injectors
could be a lot of other things too...o2 sensor, pcv valve, air filter, timing is off,

I would try some seafoam (Im in love w/ it now) and then change the plugs and oil+filter. - read my post on how its done.

Have you been using the same type of gas?

You could also just try resetting the ecu...sometimes that helps, i guess.

[AzCivic]

10bucks doesnt buy as much gas as it used to, did you not notice the increase in prices?

[ebpda9]

Originally posted by AzCivic
10bucks doesnt buy as much gas as it used to, did you not notice the increase in prices?

^ agree with him

I never considered the fact that it might be 'gas prices going up'. Maybe it's because that's retarded No, this is engine related. I've been using the same 91 octane gas and putting the exact same amount in each time recently, which was 3.0 gallons, just to see how my mileage was. and substancially was decreased as opposed to 3 weeks ago and what 3.0 gallons would do.
Ok so i've taken into consideration that maybe i gapped the spark plugs wrong. But lets say that isn't the problem, what's the next thing to check? and how to check them. i need to know HOW to as well come on, i need a diagnosis here!

[pdiggitydogg]

try some seafoam

[AzCivic]

stop using 91 and put in the 87 that you car needs then you can put in more gas for the same price.

did you take into consideration a/c usage?

[bent_remy]

have you made any mods since you noticed your mpg go down?

[JDMFantasy2k]

why would you bother gapping plugs when you can just buy pre-gaped ones for cheap $$, less headaches.

[pdiggitydogg]

what??
You should ALWAYS check the gap of your plugs when putting new ones in. I dont care what the box says. They probably arent right...close maybe.
They dont come un-gapped and if they did why would they cost more? Gapping them takes like 5seconds if that.

It does pay to get decent plugs, by the way. - ie ngk

yea, i trust something i gap myself as opposed to a machine gapping something. No mod to the car (that effect mileage) ac useage is not the cause of this. guys, this is VERY noticeable, this isnt a few miles we're talking about because the AC was dicked around with. this is a significant reduction. But, the first two things I am going to do, are check the plug gaps, the air filter and the other stuff mentioned.

"stop using 91 and put in the 87 that you car needs then you can put in more gas for the same price."

uh... what?

i see what you are saying. but higher octane=more mileage. it's what i've been needing to do to get around. rather than putting 87 octane and getting hardly anywhere. get the picture? maybe if my car was working fine id use regular gas.

[pdiggitydogg]

youre not going to get better mileage out of higher octane
switch to 87
The standard civic is designed to use the lower rating (because it doesnt need to use higher)...its the proper fuel.
Youre just wasting money dude.

Octane myths

High octane gasoline improves mileage.
In general, if your car is designed to run on 87 octane gasoline, high octane gasoline will not improve mileage. If switching to high octane gasoline does improve mileage, you might find that a tune-up will give you the same improvement on 87 octane gasoline.

High octane gasoline gives quicker starting.
No, it doesn't.

High octane gasoline increases power.
If your car is designed to run on 87 octane gasoline, you shouldn't notice any more power on high octane gasoline. Again, if it does make a noticeable difference, you may need a tune-up.

[AzCivic]

Originally posted by Mischief(LTS)
yea, i trust something i gap myself as opposed to a machine gapping something. No mod to the car (that effect mileage) ac useage is not the cause of this. guys, this is VERY noticeable, this isnt a few miles we're talking about because the AC was dicked around with. this is a significant reduction. But, the first two things I am going to do, are check the plug gaps, the air filter and the other stuff mentioned.

"stop using 91 and put in the 87 that you car needs then you can put in more gas for the same price."

uh... what?

i see what you are saying. but higher octane=more mileage. it's what i've been needing to do to get around. rather than putting 87 octane and getting hardly anywhere. get the picture? maybe if my car was working fine id use regular gas.

[AzCivic]

do you drive around with the a/c on all the time or not? a/c makes a huge difference in gas mileage. your car isnt that old so there shouldnt be a problem.

[pdiggitydogg]

no doubt
you need a tune up (plugs, filters, valve adj (wouldnt hurt), oil...seafoam!)
I bet your problem would be solved...and switch back to 87. 89 at least

how many miles are on the car? I changed my 02 sensor on an engine that had only seen 25,000 kilometers, and my gas mileage went up 4 MPG!!!

48,000 about tune up time i guess :P

[AzCivic]

damn, on a 2 year old car?

yes. heated o2 sensors are supposed to be changed every 60,000 miles. Not to mention all the other normal tune up items (if they havent been done) may need to also. I would do it all, plugs, cap, rotor, wires, air filter, fuel filter, PCV valve, and o2. Just my 2 cents.

sounds good. so i guess the 02 sensor probably doesen't need the replacement yet, huh? well then seafoam is probably the first thing ill go for. since the car is (Yes) a 2002 with already 48,000 miles on it, maybe its just a tuneup thing

[AkimboStylee]

check tire pressure, and check allignment, if the alignment is off, it causes a little drag, and if the tires arent up to psi, it can cause lower mpg. check air, fuel filters and everything they said^