New to site, could use some help/tips

[maherj00]

Hi,
My name is Jim, and I recently bought a 99 Civic HX MT. It's got a lot of miles on it (175K), but I wanted something that would give me better mileage than my current daily driver (99 CRV, ~27mpg).

Knowing that the HX is supposed to be a lean burn engine and EPA estimates of 40 - 45ish on highway, I thought buying it was a no brainer. Problem is I have yet to break 40mpg. I have new 90Kmile tires (not inflated to 50psi, but higher than the ~30psi recommended), I coast down almost all hills, gently accelerate from a stop, anticipate redlights so that I don't have to come to a complete stop, drive at ~55-60mph on the highway (65 limit) and now manually cycle A/C while driving.

A few things I believe are hurting my mileage:
I just realized that the A/C is cycling a whole lot during trips, so I've been manually cycling it when I feel the need for cold air, and even then, typically only on down-hill slopes.

Also, I recently noticed that the radiator fan is cycling on/off approximately every 20-45 seconds for 30-45 seconds.... on the highway. So, I looked under the hood a little closer than I did while buying it, and noticed that my radiator fins are almost all flattened. I have a new radiator on order and while I'm at it, I will replace the radiator fan motor since it draws a huge amount of power when it cycles on.

After that stuff, I'll give it a full tune-up (plugs, wires, dist. cap/rotor, and I thought about O2 sensors, EGR and PCV).


I'm hoping that those items alone will get me above 40 - 45mpg.

If anyone has any suggestions on other things that will help get my HX from 36-38mpg to a more respectable 40-45mpg, I'd appreciate your thoughts.

Once I get into the 40s I'll start looking at other items that I see posted. My ultimate goal is to get this HX to average 55mpg on a regular basis.

Thanks for reading, posting, helping.

[MT bucket]

Looks like you are doing all the right things you should be beating the epa bigtime!
mabye when you get all the issues with the car fixed that will help.
getting a instant MPG display liker a scangauge II would be helpfull in letting you know when the most fuel is being burned to help you pinpoint where you can make improvements.

[nervousmini]

One other thing not to overlook, even though you just got new tires don't forget about getting a good 4 wheel alignment! Take it to someplace that really knows how to do a 'perfect' alignment. not just making all the red color spec green! You want to get the minimum allowable toe and camber specified for your car. This will reduce the work that the car has to do trying to drag the tires along.

[Ford Man]

You said you were manually cycling the A/C and running it on down hill slopes. In my '97 Escort wagon I have noticed according to the Scan Gauge that it is better to run the A/C on the uphill climb. (wider throttle opening less pumping losses) It does decrease mileage on the climb, but not near as much as it does when coasting down hill. If you have a straight shift try to shift at as low RPM's as the engine will let you. Highest gear and lowest RPM's are always best for FE. In my '88 Escort I can go as low as 20 mph in 4th gear (4 speed) on downhill, 25 MPH on level ground and as low as 35 MPH in 4th up hill. When going down hill get completely off of the gas. Most cars that have been made in the last 20 years have DFCO (deceleration fuel cut off) which cut the fuel off above a certain RPM when coasting. I'd also raise the air pressure to sidewall maximum. If you can rig up a warm air intake it will probably help mileage too. It helped my '88 Escort by approximately 8-10%. Next time you put new tires on it if you go to a larger tire that will help, because it will give you taller gearing. My '88 Escort came from the factory with 165-80-13's and I'm running 185-75-14's. Try to time out your traffic light so you never have to come to a complete stop. I've read that it take about 20% more fuel to get a car rolling from a dead stop than it does if you can keep the car barely rolling.

[PaleMelanesian]

At that age, your O2 sensor could very well be dead or dying. It's a pricey part ($300 or something), but without it the whole lean-burn aspect of the car is crippled.

Nice car, by the way!

[Mr. Pancake]

The car should throw a code if the sensor is dying/dead. Jim, is your check engine light on? Besides the tune-up I'd change the oil and filter (no telling when the previous owner last did this). Check your air filter too.

[drimportracing]

Welcome to www.cleanmpg.com Jim,
That's a great car to own. When you do the tune-up also change the thermostat to the highest temp that you can buy. (I run 195*) Make sure to change the radiator cap to the highest pressure. (I think mine is 17 or 19 lbs) This will make your car warm up quicker but will not overheat.

Your fan will turn on more at stoplights during the summer but when it starts to get around 65 degrees F, you can safely unplug your fan until next spring. In the unlikely event that it were to run hot, keep an eye on your temperature gauge and if it goes above 7/8th hot, plug the fan back in and turn on the heat for a minute to pull the excess off the engine. This has only happened to me when going uphill at less than 5mph for many 100's of yards (putting flyers in newspaper boxes) it was 70+ degrees outside. So unless your stuck in bumper to bumper traffic you'll benefit from the warmer temps and no fan technique. You could install a manual fan switch. but I live on the edge.

If your car hasn't ever had the timing belt replaced then it's going to be going in the next 10-20k miles. If your unsure if it's been done then do it anyway. I broke one at 189k on my first Honda and always replaced others at 180K or sooner with no problems. It's an easy job if your mechanically inclined and much cheaper than paying someone. - Dale

[maherj00]

Thanks to everyone for your replies...

With the new tires, I did have an alignment done... don't know if it's perfect, but then again, I don't know of anyone locally who will attempt to make it perfect... but it couldn't hurt to ask.

I also had the oil changed the day I bought it... and it's now due for it's second.

I also had the timing belt changed just prior to purchase (172K mi)

The check engine light does not come on and has not come on since I've owned the car. I half thought about looking at 02 sensors anyway, because at 10 years/170+Kmi, they could be way out of calibration... but who knows.

As far as running the AC on uphills, the hills here are really steep... and there' quite a few of them. Just using constant acceleration, the car can drop from 65 to 30 from base to peak. The AC draws a huge amount of power off of this engine (I think my compressor may be on it's way out), which is why I do it going down hill. It provides just enough cooling to keep my fat @$$ happy and doesn't rob me of valuable hill climbing power.

I'd like to try the scangauge somewhat soon to see if the car ever goes into lean burn, but at this point, I would venture to guess not, since I'm only getting ~36mpg.

One final note... in the last day or so, my tailpipe rusted off and now there's a big hole in the muffler. Can anyone suggest a new type of muffler? I'm assuming with the leanburn thing, back pressure is much more important than in a normal car, so is a nice smooth mandrel bent exhaust out of the question? should I go with something more stock and crush bent?

Thanks again for all of your responses... you've all been most helpful.

Jim

[PaleMelanesian]

I'd stick with stock. There's just not that much air flowing through there at low rpm, so you don't need high flow capacity. Mine rusted out like that and I had a shop weld a repair for about $50.

[R.I.D.E.]

Use recirculate on your AC, and run the fan on lower speeds. The steep hills will hurt your mpg significantly. Best to cycle the AC on on the downhill sections, especially if you have to stay in gear to keep from going too fast.

With your foot off the gas in higher gears downhill, the AC is free because you are in fuel shutoff. Use a higher gear and AC instead of downshifting to keep your speeds legal on those long downhill sections. Run the fan to high speed downhill, then kill the ac compressor and let the fan circulate the cooler air to keep it fairly cool going back uphill.

Recirculate takes less work, since it recools the cooler air and has less humidity to remove on repeated cooling cycles. The oxygen sensor can reduce your mileage to a certain extent before it trips a fault code.

regards
gary