Its a 91 civic SI with 125K miles. Stock except for a 2.25" cat back exhaust.

Good: I did a recent full tune up. Tires are brand new and have good air pressure.

Bad: I have a bad front wheel bearing. Alignment may not be to stock spec. I adjusted rear drums to have a LITTLE drag (something I was taught to do years ago).

I average 28 MPG highway driving softly.

From searching, I was expecting 35+mpg highway but didn't see close. From my bad list described above (wheel bearing, alignment and drag on drums) would that make up difference? What else?





Modified by AlphaKennyWun at 10:49 PM 6/12/2008

 

is your computer throwing any codes?

 

no

 

how olds ur o2 sensor?

 

brand new

 

well with the wheel bearing you'd be pulling to the side with the bad wheel bearing it really wouldn't effect the mpg
WHAT WOULD EFFECT YOUR MPG:
#1: if you went on the cheap side and bought a splice o2 sensor (when you cut the original wire and splice it into the new sensor) this could be a problem
#2 your coolant temp sensoer could be on the fritz (even with obd0 it still regesters to send a signal to the computer to partialy tell it how much fuel to send)
LAST BUT NOT AT ALL LEAST
you could have an exhaust leak ,yea i didn't think about it either but it happened to me and i never gave it another thought

 

all oem parts right.....

 

and fix the wheel bearing... it would not be cool if it locked up on you

 

Low tire pressure believe it or not bad diaphram on your fuel pressure regulator use denso or ngk plugs and gap to factory specs. Cap/rotor, fuel filter and time to time use a fuel injection cleaner Lucas is good stuff.

 

you said you have good tire pressure, but what is it? and what kind of tire pressure guage are you using? The stick guages are garbage if thats what you use. Sears sells a pretty nice dial type pressure guage, so you should get one.

Things that can also help are a new catalytic converter, o2 sensor as someone said, new spark plugs, perfect alignment with NO TOE, clean air filter, clean oil, driving without radio and climate adjustments and driving with the windows up, and last but not least, getting rid of dead weight, like back seats, AC system, smaller battery, sunroof glass, sound deadening, new wheel bearings all around, and on and on..

 

just a question, how are you calculating your mpg? the only way to get an accurate reading is running the the brink of emptiness, when you start getting fuel cuts when turning if reading by the gas gauge is a poopy way

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by neozero999 &raquo;</TD></TR><TR><TD CLASS="quote">just a question, how are you calculating your mpg? the only way to get an accurate reading is running the the brink of emptiness, when you start getting fuel cuts when turning if reading by the gas gauge is a poopy way </TD></TR></TABLE>

oh gosh.. long division.

fill tank to top....reset trip meter.... drive normally or whatever conditions u want to see mpg for.... fill up tank again... note how much gas needed to be added.... divide miles on trip meter by gallons of fuel needed to refill...

mpg is of course.... miles per gallon... miles / gallon

and yes... you may also cheat and use a calculator. I won't tell.

 

How about your temp. Is it showing up cooler than normal? Turn on your car cold and go squeeze the top radiator hose before it get gold. If there is water in it, then your thermo is stuck open, robbing some mileage.

 

MAP sensor perhaps. Do you ride with the windows down? you could be getting drag from something else as well. So many factors in this. And i might add a WOW for only 125k on the odo. I have 110k on my S2k lmao.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by neozero999 &raquo;</TD></TR><TR><TD CLASS="quote">just a question, how are you calculating your mpg? the only way to get an accurate reading is running the the brink of emptiness, when you start getting fuel cuts when turning if reading by the gas gauge is a poopy way </TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CRXDrew &raquo;</TD></TR><TR><TD CLASS="quote">fill tank to top....reset trip meter.... drive normally or whatever conditions u want to see mpg for.... fill up tank again... note how much gas needed to be added.... divide miles on trip meter by gallons of fuel needed to refill...

mpg is of course.... miles per gallon... miles / gallon

and yes... you may also cheat and use a calculator. I won't tell. </TD></TR></TABLE>


correct. I have what amounts to a log book that has trip odometer reading and gallons of gas pumped for every fill up since i have owned my car.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fireant &raquo;</TD></TR><TR><TD CLASS="quote">How about your temp. Is it showing up cooler than normal? Turn on your car cold and go squeeze the top radiator hose before it get gold. If there is water in it, then your thermo is stuck open, robbing some mileage.</TD></TR></TABLE>

There should be little to no air at all in the cooling system. Air bubbles messes with the temperature sensor.


Janos

 

why do you want drag on your brakes? that would hurt gas mileage

 

All OEM parts except plug wires
NGK plugs
Bosch O2 not spliced
cheap-o tire gauge to around 32-34 psi
water temperature is fine
No exhaust leaks
transmission oil blend of Royal purple 10-30w and Syncromax


I like that way of calculating miles rather than run on the brink of emptiness which is what I did.

I know the wheel bearing and rear brakes are probably causing friction and drag. Oh did I mention I use heavy 20-50 oil?

The cheap-o tire gauge is probably not at all accurate either. I always run A/C because its HOT in Miami. Replacing the catalytic is a good idea.


Your tips definitely give me a good places to start. First i'm going to fill up and recalculate the miles. I'll post back here with results

125K because the original owner drove two miles to work round trip for first 16 years.


Modified by AlphaKennyWun at 11:18 AM 6/14/2008

 

lazy *** could have walked it lol. How long have you had the car?

Why are you running oil that thick?

Janos

 

wrong tire size. too heavy oil, Timing off. Old motor. I would replace the thermostat. you never know.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Janos Lin &raquo;</TD></TR><TR><TD CLASS="quote">lazy *** could have walked it lol. How long have you had the car?

Why are you running oil that thick?

Janos</TD></TR></TABLE>

Only a few months. The motor is leaking and burning oil. I suspect the oil pan gasket, valve cover gasket and a clogged PCV valve. I doubt its the rings but you never know.

 

And you wonder why you're getting 28mpg? LOL This is like you telling us that you removed your mirrors, did a radiator block, over inflated your tires and do Pulse and Glide in order to maximize your mileage but confused about the abysmal mileage, only to later mention that you're running thick as hell oil because you're burning oil.


Address the burning oil issue first, do a major service aka Tune UP (replace all seals and do valve clearance check, PCV valve, sparkplugs, etc. etc.), fix that bearing in the front wheel and then we'll talk.

Edit: you claim you did a tune up yet you didn't do any of the things I just mentioned in my post? How is that a tune up? What, you replaced the air filter, added thicker oil and called it a day?


Modified by imzjustplayin at 5:35 PM 6/15/2008

 

Given what the last owner did, I'd say it needs an Italian Tuneup. Drive the car til it's at E, dump a full bottle of fuel injector cleaner in there, add 3 or 4 gallons of gasoline. Then drive it like you stole it :D I recommend 2nd or 3rd gear pulls to redline up a nice, steep hill a couple times. It'll help clean out whatever crap there is in your engine. It needs heavy load wide open throttle pulls uphill, and the downhill gives it a nice downhill engine braking as well. Replace your PCV valve also if you haven't. I'd also do a Seafoam treatment as well.

If that doesn't fix it, then take out the spark plugs, turn the crank until all of the cylinders are about even at the middle of their stroke, and pour about a cup of ATF down each of the cylinder bores. Let it sit at least overnight, a full day would be better. Then using a turkey baster, draw what oil you can back out, then stick some paper towels down the spark plug tubes, try not to pack it down too much, then rotate the engine by hand a few times. Take out the towels, and cover the valve cover with a bunch of rags or towels, something to weight em down would be good, and crank the motor until it stops spitting out a lot of oil. Stick the spark plugs back in and take her out for a drive. Be mindful, you'll probably spew smoke for a bit as whatever oil got down the headers burns off. The ATF tends to break down varnish and crud that's clogging up your rings, and preventing them from working correctly. ATF is a lot more aggressive than engine oil at cleaning things up, but bad for continued use internally.

Do a oil change, with the correct weight of oil after either of those. That should hopefully return your car to a good state of operation.

Janos