surfingisfun001

I have a 1995 Honda Civic Hatchback VX. The stats online for gas mileage say 44 city / 51 highway. I've seen higher and lower listed online. The lowest I've seen is 40 city. Currently I am getting an average of 28 mpg city. I have only taken it long distance on the freeway once and got 39 mpg. While this is still pretty good and I'm not trying to complain I'm wondering why I'm getting 28 city/39 highway and not higher. Anyone know why this is and if there is anything I can do to improve the gas mileage?

B20VtecVillain

Basic tune up items all influence fuel mileage. If it has not been done recently, change the fuel filter, spark plugs, plug wires. Also check the O2 sensor for proper operation as this would absutely effect gas mileage while driving around town. Is the exhaust system factory original? A clogged cat can also cause lessened MPGs. Also, try running a can of Seafoam in yor tank at the next fill up. Cheap and fairly effective means of cleaning up the injector spray pattern of they are getting clogged.

B20VtecVillain

Also take a quick check on your wheels and suspension components. Poorly inflated or improperly sized tires, stiff wheel bearings, brakes that are hanging up slightly etc will all add drag and make the engine have to work harder to move the vehicle and therefore decrease mileage. Take your driving habits into account as well; if you are driving with any type of heavy throttle foot you will never achieve max mpg, and I would imagine a stock VX needs to be pushed to merge/change lanes etc so take that into account as well.

surfingisfun001

Thanks for the feedback. When I bought the car the odometer read 175,000 miles. Later I found out the cluster was replaced in 2004 and the car actually has 350,000 miles. I'm not sure if this could have something to do with it. It is all stock and seems to have been well taken care of and was mainly owned by one person throughout its life. I have recently replaced the fuel filter, spark plugs, 02 sensor, and have run a can of seafoam through the tank. The exhaust, engine, and everything else is all 100% stock. I'll try checking the cat. Thanks.

surfingisfun001

I will check all that as well, thanks. I drive pretty mellow and average, not fast at all. I have tested it driving both with a heavy foot and mellow.

B20VtecVillain

Aside from that, with 350k that mileage seems pretty good. Doing a compression and leak down test would let you know for sure, but I'm willing to bet after that long of a service life there is a good deal of wear on internal components which would make the engine less efficient than when it was fresh. All things considered I think she's giving you close to the most she can at this point In life. 20 yrs old and 350k miles definately classifies it as a "senior" lol

surfingisfun001

lol yeah. I ran a compression test and it came out surprisingly well. It could simply be that it's old huh?

B20VtecVillain

Yea, the less efficiently the engine can make its power the harder that engine will have to work to move the vehicle at a given speed and thus the more fuel it will consume getting you from point a to point b.

surfingisfun001

That makes sense. Thanks a lot for the feedback.

TomCat39

The VX has an EGR. If it's not working properly it can adversely effect your fuel efficiency.

I didn't see it mentioned to clean out your EGR. That too should be added to the list.

With 350K on the motor, it's likely not going to be as effeicient as it was when new.

I still think unless the rings are almost totally gone, you should be hitting mid to high 30's for city and 40+ highway.

My D15B7 non vtec motor is averaging 33 mpg mixed driving. I shouldn't be beating you in MPG. Not by a long shot.

surfingisfun001

Ok I will definitely check that out thanks. Come to think of it when I first got the car the check engine light came on and the code was for the EGR lift. I took it to the mechanic, I don't know what they did but the light hasn't come on since. I'll look into that though.

B20VtecVillain

Forgot the VX has an EG recirc, definately clean and make sure the valve functions as it should. I think a lot of it comes down to the manner of driving though. There are many different variations of "city" driving. Stop light every 30 secs like in an actual city such as a NYC, Philly etc is different than stop and go in a less congested urban area. Also, driving habits will always at a huge role. It is a rarity to achieve the full mileage exactly as advertised on the EPA sticker regardless of engine condition.

surfingisfun001

Yeah true. I'll check out the EGR, thanks.

TomCat39

Agreed, however, my 33 avg is with both an aggressive lead foot on many occasions (love the sound of my car) and also I have severe stop and slow rush hour to and from work. A normal 40 minute commute is more like an hour.

I'm thinking the VX driver isn't going to drive as lead footed as me so I really should not be beating them out on fuel efficiency as I am not driving in the efficient manner one should.

My average is a true mix as I also have country roads around me that I drive frequently which is more in line with highway cruising. So with my lead foot, stop and slow and country driving, my 33 MPG avg is truly mixed driving. A VX should blow that out of the water without even trying.

baller status

My VX has 307k miles and I consistently get 45mpg mostly street driving. The worst mileage I have gotten is 33 when I was rushing home on a road trip maintaining 80+ mph up and down hills on a windy night. The best I can get is 49 mpg.

First do the maintenance, then do the deep maintenance. Deep maintenance includes things like doing a valve adjustment, calibrating the TPS, removing and cleaning out the intake manifold, removing and cleaning off sensors, etc.

Tires are usually the biggest culprit. The type of tires, condition and pressure. Overinflate your tires to 38psi and check the pressure frequently. Oil changes, ignition timing, O2 sensor, make sure the cat converter isn't plugged and that there are no exhaust leaks, lubricate your caliper pins, replace your wheel bearings if they drag too much...

slogfilet

iTrader: (1)

You mentioned you replaced the O2 sensor... what brand/model did you use, and how much did you pay for it?

The VX requires a very specific sensor, as it is critical to lean burn operation.

The cluster was swapped, is there a chance anything else has been swapped? ECU? Are you positive you have a D15Z1 engine?

surfingisfun001

I will check all of these things in the near future. Thanks for the info. I see you specialize in car security features. My last civic was stolen and I have installed a few goodies into my new one myself.

surfingisfun001

I am not sure, my mechanic installed it. What is the name of the sensor that the VX requires? I can try checking to make sure.

I don't think anything else has been swapped but it's hard to know for sure. It is in fact a D15Z1 stock engine, yes.

slogfilet

iTrader: (1)

The OEM sensor is $300+. There is an NTK sensor that is a known good replacement (model 24300). The wrong sensor will mean it's not going into lean burn... definitely worth looking into the specific model number you have.

surfingisfun001

It says "Denso O2 sensor" with the number being 234-4099. Amount was $70.43.

slogfilet

iTrader: (1)

Do you know if you have a Federal or California edition of the VX? That sensor is not correct for the federal version. You should be able to determine which edition you have by the VIN. How many wires are coming off the O2 sensor?

TomCat39

Straight from someone knowledgable on amazon.com

"The NGK (really NTK but its all the same) 24300 is the 5-wire O2 sensor for the civic VX from 92-95. "

While the 234-4099 appears to be the 4 wire for the 92/95 CX/DX and others have reported this working on their 2000 civic.

I think you may have the wrong sensor.

You can get the 5 wire on Amazon.com for 159 bucks:



It's 211 on Amazon.ca



The price of the 234-4099 is 30 bucks on amazon.com and 40.19 on amazon.ca. Definitely the wrong sensor.

slogfilet

iTrader: (1)

Helpful! We just need to make sure he indeed has the federal version that calls for a 5-wire sensor.

Is the actual connector different on a 4-wire vs. 5-wire sensor?

TomCat39

Good point. Even though I thought the 5 wire was required regardless of jurisdictional legislation for lean burn as the VX ECU needs the wideband to be able to do lean burn mode properly. I didn't think the VX could operate properly without a wideband O2 sensor.

Not really sure and my ETM is at home for the 92-95. I can check it once home.

slogfilet

iTrader: (1)

The Cali edition doesn't have lean burn due to emissions regulations... it gets slightly lower mileage and uses a different O2 sensor (since wideband isn't needed). Off the top of my head, I can't think of any other differences...