mililani

So, I'm a little miffed. After being told constantly on these forums that an old o2 sensor could cause deteriorated gas mileage, I finally got around to changing mine. I have an 01 Civic LX with 155k miles on it. It used to get around 44 mpg HWY, but that slowly deteriorated to 38 mpg HWY. I bought new tires, because it was time to replace the old ones, and still getting the same mileage--no surprise, really. Then I decided to change out the o2 sensor with an OEM part. Lo and behold, my new sensor has made my gas mileage even worse. I'm getting 32 mpg HWY. WTF?? So, I'm putting back in my old o2 sensor and see what is going on.

Anyways, I'm kinda pissed that this was $70 down the toilet. Does anyone here want to buy a slightly used OEM front o2 sensor?

mikey1

so let me get this straight.....you are disappointed with 38 mpg?

i would say thats pretty damn good

a lot of different factors come into play with fuel mileage, changing an o2 sensor and hoping it will increase your fuel mileage by 6 mpg is unrealistic to me, unless the o2 sensor was faulty and supplying a CEL and code (which im assuming yours was not)

do you live in a cold winter climate?....cars in general use more gas in colder weather, people warming them up longer, etc etc

lowlife9

dat winter gas blend doe.

ezone

I'm upset that my in-town daily commute mileage went from 28-29 down to 24-25 in the last month.
That's like almost 33%u2153% drop!


Da pricea dat gas doe.



EDIT: Damn, that was supposed to read thirty three and one-third

lowlife9

dat led foot civic race car doe.

ezone

Just did a highway trip outta state. Got a whopping 30 MPG on the way there. At 80+ MPH.

Return trip at 75 MPH with drafting offa traffic most of the way, I managed 35 MPG.



Soopacheep gas inna nex state doe.

lilrob1213

So did putting the old o2 sensor back in help??

mililani

Some updates: the new O2 sensor is now working as well in terms of fuel efficiency as my old sensor: 38 mpg. So, I'm going to just get rid of it. I think the initial bad fuel efficiency was a one off fluke. I'm going to swap it out with my old O2 sensor and see how that goes. Then, I'll probably sell the new one online.

I think my diminished fuel efficiency has to do with the crappy 7th gen transmissions. Mine has been slipping for quite a while now: the past 40k miles. And, I know before it used to cruise at 65 mph at around 2k RPM's. Nowadays, I need to get above 2600 rpms to get around 65 mph. For the same engine, that means there is loss of power transfer somewhere. It's most likely the drive train.

By the way, our 2009 Honda Civic LX gets 42 mpg HWY right now. That hasn't changed with different winter/summer blends. I live in California, so I'm not sure we have much of a change up in the winter. It has more HP than the older 7th gen Civics, so the lower HWY economy is a bit expected. It cruises at 65 mph at just under 2k RPM's. That is why I'm thinking my older Civic is having problems with power transfer somewhere in the drive train.

Anyways, I'm thinking about taking out my transmission and rebuilding it myself. Does anyone know of any books/manuals that are about rebuilding these things? I've replaced transmissions before on my own. I wouldn't mind trying to rebuild one.

mikey1

i find this very hard to believe,


this seems normal to me (for an automatic),

i have always been around 2,800 at 70mph (auto)

ezone

Winter fuel change happens there too, it's nationwide.

exiled1

My 2002 Civic EX v-tec would get 34.5 -35 mpg. I got the auto trans rebuilt for around $2K. new cat and for and aft o2 sensors and short ram air intake. now I get around 38 sometimes push 40 if i drive mild. Don't think the new cat and os sensors made much difference but the rebuilt trans and the short ram intake K&N definitely did. I keep close track of my fuel millage on gasbuddy cause I commute about 80 miles a day. I also run Yokohama Avid low resistance tire at 34 psi cold. Also took out the back seat.

lilrob1213

How much you want for it?

bsmiley

I bought an NTK in October. Amazon had it for $23.70 & the Denso was $34.