honda civic dx - very poor gas milage

I just bought a 94 honda civic dx 4 door sedan with 154k miles. I saw
on edmunds.com that they are supposed to get inbetween 35 and 40 mile
per gallon, but I get about 32 tops. I'm the only one who uses it - no
passengers, or other weight for that matter, the car is very clean
inside. I replaced the spark plugs with bosch platnum 2's (you don't
have to adjust them i heard - correct me if I'm wrong). I usually run
lower grade gas (87 or so). Tire pressure is fine. Other thoughts
are:
- new air filter (would probably get a K&N ram air - good idea?)
- new spark plug wires (the ones I've got are fine except I noticed a
small amount of oil on one which I cleaned off)
- bosch platnum 4's (any better than bp 2's?)
- change transmission fluid
- oil change

spend about $75 on fuel a week and bought this car because of gas
milage - help!

 

My thoughts:

Manual or auto tranny? On this version, the manual gets better mileage.

Are you a lead-foot driver? Aggressive driving hurts mileage.

I am skeptical of Bosch spark plugs. I would use OEM plugs (NGK or ND).

I would avoid K&N air filters. Some of these have been known to cause
problems with Toyotas. Not sure about how they would affect Hondas, but I
would just get an OEM air filter.

Is this all highway driving, or was there some city driving too?

If the weather is getting colder, that will decrease your mileage.

 

----------------------------------

The Bosch were a poor choice. . . Anyway,

It may seem obvious to most folks around here, but I'm still amazed that
people have a hard time figuring mileage. What method are you using for
your calculations? Please be very specific.

'Curly'

 

Like Curly said, cold weather may be playing a role. But two
other candidates for replacement for a car this age are the
PCV valve and the O2 sensor. While both may operate
satisfactorily after years and many miles, their operation
may not be optimal. Buy only OEM for each. Should run you no
more than about $25 for the PCV valve from your local dealer
and $80 for the O2 sensor from
https://www.automedicsupply.com/ . At a minimum, remove the
PCV valve, spray it with PB Blaster. Wipe down, replace it.
If you found significant waxy buildup in the PCV valve, then
just cleaning it may make a big difference.

I can't tell from your post: Do you have new ignition
wires? If they're old and you have a digital multimeter, do
a resistance check on the ignition wires and report back.
Are the wires OEM?

If you're getting oil in the spark plug tubes, say so. I
have a resource to help with this.

I don't think platinum plugs make a difference in fuel
mileage for this car, based on general reading as well as my
own experience with both in my 91 Civic.

Does the owner's manual okay Bosch plugs for your Civic? I
don't think mine does. I use NGKs.

Consider a new distributor cap and rotor, too.

Elle
Original owner, 1991 Civic LX, 172k miles, manual
transmission, no air conditioning, 40+ mpg for most of the
year.

 

Consider also:

-- replacing the fuel filter

-- putting a bottle of Chevron Techron (an injector cleaner)
into the fuel tank, too, per the bottle's directions.

-- Doing an air purge of the coolant system and making sure
it's filled to the proper level. If time allows, change out
the coolant, unless you know it's new and OEM or orange
Dexcool.

 

First some perspective. If you were getting 37 mpg, you would be
spending about $65 per week. Significant savings, but not huge.

I would not use a K&N filter, they let a lot more dirt go by than
stock. A new stock filter might be in order if the old one looks
dirty. If the plug wires are original or aftermarket parts you might
want to replace them with Honda wires but don't expect any measurable
improvement in mpg. I would use the specified NGK plugs also. Change
the oil and transmission fluid if it is time, or if you don't know
when it was done last. None of this is likely to measurably affect
mpg, unless the car is not running well to start with.

You have to consider how you drive the car - city or highway, flat or
hilly, fast or slow, how much braking. Also, unless you live
somewhere close to the sun, the temperatures are getting cold now and
that will hurt milage. If you are driving 100% in a northern city,
heavy foot on gas and brake I would say 32mpg is pretty good. If you
are doing 90% highway miles at 60mph then 32 mpg would be mediocre but
not "very poor."

 

is it a 5spd? or automatic? the auto is rated 29/36, so 32 isnt bad.

my CX is rated 32/37 and i get about 32 regardless. i dont lose sleep
over it.

does it have the same size tire on it that it came from the factory
with? check your door jamb sticker and compare to whats on there.

a taller, skinnier, harder compound tire would give better mileage.
thats why mine came with 175/70-14 from the factory. firestone FR680s.

i replaced em after 6 years, even though they had a lot of tread left.
got some 185/60-14s and it handles much better... but i lost an mpg or 2.

more air needs more fuel to burn. people buy em to race or rice, not for
economy

NGK or ND plugs wouldve been my first choices

if all you care about is mileage, a subaru justy or geo metro of that
era would have been a better choice. or a jetta or benz diesel.

hm... 75/$2.30=32.6
32.6*32=1043 miles/week
1043/5= 208.6miles/workday

if i was driving 200 miles to work and back 5 days a week, id be looking
for a job closer to home i love my honda, but i dont wanna spend 4
hours a day in it.

you DO realize thats 52,000 miles a year, right? how long do you think
that 154k mile civic is going to last?

 

Maybe more. Did you factor in odometer error? A smaller diameter
tire will register higher speeds and more miles than it is really
traveling.

 

Manual

Actually I just purchased bosch platnum 4's today (oops) oh well - no
harm done

mostly highway miles

 

I filled my tank (till the pump turns off) and then reset the trip.

When it is time to fill up I do the same, then divide the miles on the
trip odometer by how many gallons purchased on the recept - I do this
to the 1000th decimal place since that's how acurate the gas pumps are.
This should get a perfect reading.

 

Actually Today when I was replacing my spark plugs I noticed there was
oil in the plug tubes. The guy at the auto parts store said that is
caused from not tightening the valve cover - since I just replaced the
valve cover gasket. My question is what to tighten it to? I have a
torque wrench.

Also, I haven't done anything with the ignition system and I believe it
is stock.

 

First, I would replace the PCV valve, distributor rotor and
cap, and ignition wires. Use only genuine Honda parts.
(That's what OEM implies: original equipment manufacturer.)
The new ignition parts will help preserve the igniter and
coil (which are within the distributor) too. The igniter and
coil are expensive and do fail often on Hondas, unless one
is obsessively careful about maintenance. So the latter
distributor parts are a great investment for only $100 or
so. If the ones in your car are old, then replacing these
parts should make a noticeable difference in fuel mileage.

See my site
http://home.earthlink.net/~honda.lioness/id3.html for the
two most common causes of oil in the spark plug tubes for
1990s Hondas and how to remedy them. Your auto parts store
guy is a little off. There are gaskets in the tubes
themselves that fail over time. But one does have to remove
the valve cover to get to them. The valve cover nuts are
tightened to only 7 ft-lbs. Be very careful to tighten as
evenly as possible.

For a complete manual for your 94 Civic, including many, if
not all, torque values, go to http://www.autozone.com . On
the left, click on "Repair Info," then "Vehicle Repair
Guides." Click on car year, make, and model, etc.

Note: In the manuals and at online parts sites, the valve
cover is also known as the "cylinder head cover."

When driving, my understanding is it's best not to coast but
to keep the car in gear. Letting the RPM fall below a
certain low value results in the engine control system being
less efficient. My anecdotal experience with my 91 civic's
manual transmission seems to support this.

 

I heard that if the pcv valve rattles when shaken, it is still good:
let me know if this is true.

Ignition wires = spark plug wires? I know I'll be getting new spark
plug wires soon, is there a particular brand that is better than
others? Also: would it be worth it to throw away the bosch platnum 4's
and get ngk plugs? (everyone obviously likes ngk's, but are they really
that good? I bought the platnum 4's and installed them in the parking
lot - I would've got ngks otherwise)

How often should the valve lash be inspected? This is what annoys me
greatly - I just replaced the valve cover gasket, and still I get oil
in the tubes. The gasket is good, why does it make any difference if
it is tightened too much. I put some sort of gasket sealer on the
bottom side of all the gasket (the top has a lip which goes up into the
cover), should I tear off the cover, clean and put on new sealer on top
and bottom of gasket?

Here is a list of most of the repairs that I'm thinking of doing so
far, let me know which are more important:
air filter
distributor cap & rotor
spark plug wires
fuel filter
O2 sensor
PCV valve (if it doesn't rattle - correct me if wrong)

Anything else?

Oh - my tires were 175/70 13 on steel rims. I now put some rims/tires
from another car on the front because of the snow but I'm going to get
new tires on the steelys. Is 175/70 13 skinny/tall enough tire for
good mileage?


Oh - I just reread SoCalMike's note about how long I think this civic
is going to last. There are roumors of an accord and a camery getting
up to 1,000,000 miles - the camery was bought back by Toyota I believe.
I'm not hoping for keeping my car for that long, but I'm running high
mileage rated synthetic and doing everything possible to make it to at
least 300k or 400k. I started another topic called: I want to run my
civic to 1,000,000 miles - please help!

 

oh, yeah. they tend to be the cheapest, made of the hardest rubber too.

 

Doesn't matter, the engine probably had to put in about the same amount of
work, regardless of the tire's offset.

Pars

 

Wow! 200miles/day!?!. I'd want to keep the time spent on the road to a
minimum. If I were you, I'd drop the weakly 1.5L engine in the 94DX and get
a 96+ DX with a manual tranny. By trading up, you get a bigger and more
robust engine. The 5spd 96+ Civic is able to cruise at 85mpg and return 32
mpg which should shave on the fatigue factor.

Also, It would be wise to splurge on the tires (unless you've got a big life
insurance policy and you're in a rush to meet the next life). That much time
spent on the road while holding down a regular job is a bad mix. So, keeping
the vehicle as safe a possible is a priority and fuel consumption secondary.

For Maintenance;
-At 50,000 miles/year, you'll need a timing belt change every 2 years.
-A tansmission oil change annually.
-If you're using synthetic, I'd change at every 10,000 miles and Rotate the
tires everytime you do an oil change.
-If you get winters, get 'ice' tires ('snow' tires for us Canadians)

Pars

 

It could be leaking at the O-ring gaskets under the rocker assembly.
Mine was and the old O-ring were brittle and not rubbery anymore.

 

It's not necessarily true. For one thing, there's a spring
in the PCV valve. After years of being compressed and
decompressed, the spring doesn't apply the same force for
the same deflection. Other internal parts may wear as well.

With the car running, you can wrap the rubber hose going
into the top of the PCV valve in cloth and then squeeze at
this point until the hose is shut. Wait about 30 seconds.
You should hear a click, which indicates the valve is
operating at least somewhat. But it may not be operating
optimally.

Here's a drawing of your car's PCV system to help:

http://www.hondaautomotiveparts.com/auto/jsp/mws/prddisplay.
jsp?inputstate=5&catcgry1=Civic&catcgry2=1994&catcgry3=4DR+D
X&catcgry4=KA5MT&catcgry5=BREATHER+CHAMBER

Buy genunine Honda spark plug wires. Get them at a dealer or
an independent shop specialized in Hondas that says it sells
only genunine OEM Honda parts. Or buy them online at the
site above.

It's not so much that people like them. It's that the manual
says use them (and I think one other manufacturer's plugs).

I don't know if it's that big a deal. Maybe someone else has
an answer. If someone else doesn't, then I guess I'd leave
the Bosch's in for at least two years or 30k miles,
whichever comes first to get some money out of them.

Did you read the web site which I posted??

That gasket isn't what causes leakage into the tubes. It's
another set of gaskets that cause the leakage.

Uneven tightening of the valve cover will tend to cause the
gasket to not seat properly, allowing oil to leak down the
exterior of the engine.

Once you get the valve cover off, you'll see that it's a bit
of a finesse job putting the gasket on and tightening
evenly, so the gasket seats properly.

Move the O2 sensor to the very bottom, and don't replace it
until you've replaced the other things and seen if your fuel
mileage improves. You might get a few more years out of the
O2 sensor. (Alternatively, if you're feeling rich, go ahead
and install a new O2 sensor.)

Put a bottle of Chevron Techron ($6 or so) into an near
empty fuel tank just before fill-up.

That's it for now. After more miles and years you might have
distributor igniter and distributor coil problems, but then
the car flat-out won't start. The better you take care of
the other items (the ones you list above), the longer the
coil and igniter should last.

 

probably a bit more work, since the new tires are wider and stickier

 

You bought an eleven-year-old car and expect like-new "55 mph book" mileage?

I have a bridge that I want to sell you.